Seeing as I've had my car for 4 years and made a few changes thought i'd detail them here.
So i bought my (MY 2000) 330Ci SE in 2006 with 46k miles with a FBMWSH. These 2 pics show how the car looked when i bought it.
Since that time the key changes are as follows (not necessarily in this order):
M3 replica mirrors. I had one of my mirrors smashed off so i bought replicas for less than 1 mirror from the dealer. Got them painted from Chips Away (who are crap) and fitted them myself. After a year the paint started to peel, so i know never to go back there again!!
M3 Bonnet/Hood & Replica Front M3 Bumper (Aug 2007): ISome moron thought it would be fun to stick what looked like a pik axe through by bonnet, it went straight thru into top of the washer bottle! A few weeks later whislt i was debating whether to get a new bonnet or have it repaired som very considerate white van driver decide to reverse into the front right of my car, the car was still driveable no major damage, but wing and bumper need replaced. I had been looking for a replica M3 bumper anyway so this was the obvious time to buy one and have it fitted. Someone mentioned that if i was going to need the bonnet replacing then why not find an M3 one. I wasnt too bothered, but found one on EVOtechnik forums, which i got for a total of about £200. I'm so glad i did, as it looks much better. The repair i got done from AC Taylors Coachworks who did a so-so job. It took them a fair while to do the job, they accidently cut my sidelight wires. But worst of all after less than a year the lacquer started to peel right off, but they did put it right and i've not had any problems since.
Smoked Rear LED Lights (April 2007): I felt the rear needed freshening up so I bought and installed these. They are made by Eagle Eye and do have bulky resistors packs to prevent the bulb out warning light coming on, but I just tucked these away behind some trim. Had them for over 3 years now, and not had any problems.
Umnitza P46 Xenon Headlights & Predator Chromiums
My car had halogen headlights incl halogen reflectors, so to freshen up the front end I got these from Umnitza in the states, for approx £350 inlc P&P. Had a few issues with a dodgy halo ring ballast, and so they sent out a new one. With regards to reliability after 2 yrs one of the xenon ballasts failed as did 1 bulb. On a cold start on a cold or wet day some of the halo rings do take while to come on, but i have since soldered the connections rather than wire tapping them and this is no longer a problem.
Tinted Rear Windows: Got them done from Pentagon tints, quite steep at £165, but i knew they would do a good job.
Sprint Booster: Sharpens up the throttle response and makes the car 'feel' quicker, but of course doesnt actually add any bhp. I really liked this mod whereas others feel its a waste. The following is a thread i made on E46 Fanctics about my opnions on it:
http://forum.e46fanatics.com/showthread.php?t=522587&highlight=
Remap: Not so worthwhile after i had the sprint booster fitted, but it did remove a few flatspots in the power band........ or that could be the placebo effect!
Muffler/Backbox delete: Probable one of my favourite mods. I'd always felt my 330 was a little too quiet and refined so i did a but of research but didnt want to shell out £300 for an exhaust that i may or may not like the sound of. And at £70 from RMS Stainless it'd probably my favourite mod. RMS stainless are based near prestiwck and the owner is very sound and honest guy. Heres a link to a youtube video of my car and to a thread, again on E46 Fanctics:
http://forum.e46fanatics.com/showthread.php?t=573862&highlight=
H&R Cup Kit Suspension
As my car is an "SE" the ride height is a little higher than i would have liked, so i had these installed, giving a 35mm front and 20mm rear drop. These are the comfort springs & Shocks combo, costing £400 as opposed to the Sport Cup Kit which gives a greater drop (55 & 30 i think). I had my these as well as various bushes and both front control arms replaced for ~£250 by BM Motors near Carluke. This guy is a BMW specialist and very decent, honest and does good quality work. Dont let his back garden garage/workshop put you off.
I did toy with Eibach Pro & Koni FSDs, but that combo didnt give as much as a drop. In addition I hadn't noticed any worsening in the ride comfort, it was as before.
M3 Steering Wheel:
Bought off ebay. It can be a bit fiddly to remove the steering wheel, heres 2 good DIYs, the 2nd is for the E90, but its essentially the same:
http://www.e90post.com/forums/showthread.php?t=11825
http://kinmak.com/?page_id=88
LPG/Autogas Conversion: I decided last September 2009 to have my 330 converted to LPG. There were a number of reason why I decided to go this route:
No. 1: I've been sending off oil to be analysed by Black Stone Laboratories for approx the last 25k miles and this had proven that its a healthy engine (I'll post the PDF files soon), with no coolant or water or fuel dilution.
No. 2: I can't consider getting another car till at least Aug 2011 when I will be self employed and thus make it financially more viable, and I calculated that I would recoup the initial outlay of £1600 in under 2 years.
No 3: I know my 330 inside out, its mechanically sound and if my next car was to be something like a Porshce Cayman or BMW M3, i wouldn't want to drive that car everyday, and so my LPG 330 could be my daily run around, and my 2nd car could be something a bit more exotic. And because the 2nd car wouldn't get driven too often (< 6k per year) maintenance costs would be reasonable.
No 4: I've always had a hanckering for a track car, and until recently i was eyeing up pre VANOS E36 325i's. But i currently dont have a driveway or garage. So i thought why not use the LPG 330 as a daily runner when i get my 2nd car what ever that may be, then when possible in the next 3-4 years gradually turn the 330 in to a track car? And why not? Like I've mentioned I know its mechanically sound, and its the most powerful non M3 E46 ............ sounds perfect to me!
Why didn't i go this route earlier? I wish i had! Prior to converting i always thought i would replace my 330 come Aug 2011, so didnt think it worthwhile to shell out £1600 for the conversion. But when I actually sat down and thought about track cars, and the car i would buy come Aug 2011, I come up with the above plan and it made sense.
As for the conversion itself. Well i went through a company called Greenfuel and they have installers around the UK. My allocated installer was Martin Motors in Muirhead, Glasgow. But I had a few teething problems with the mapping initially, with it switching over to petrol whilst under hard acceleration, which required a few return trips to sort, but did evenetually get sorted.
Other Mods:
Smoked front Depo Indicators
Carbon Fibre Front strut brace (ebay)
Rear trunk/boot lip spoiler
3rd Cold air intake mod link to E46 Fanatics of my DIY.
In car gadgets N95 running TomTom software, N95 holder, OBD scope on N95, GROM Audio: link
Interior LED lights (from ebay):