
Originally Posted by
mimalmo
Nice car! The E46 non-M cars are fairly maxed out at the factory. You'll see small gains in performance that will be hard to feel. Doing every performance mod out there may net you an additional 15-20 hp. Programmers always say 10-20hp, the exhaust mfrs say 10-12, the intake guys say 5-8hp, etc. The problem is that they won't all add up to 50hp. It's been documented time and again on Bimmerforums, E46 Fanatics, etc. I sold my E46 ZHP earlier this year so I also know firsthand.
Here's what I would do:
Suspension - sway bars, coilovers,upgrade all the suspension bushings, stick with your current lightweight wheels or get something even lighter and do the VANOS and DISA fixes.
FInd out when the cooling system was last overhauled. If you are at 100k miles or more and it hasn't been touched, order the parts and do it before anything else. If these motors overheat, game over. Expansion tank, water pump, hoses, thermostat and refill with the correct BMW coolant (no you can't use the regular stuff from Autozone).
A properly maintained E46 with the 6 speed should last a long time but the regular maintenance is not optional.