That's a great question.. I need to do a few things in the coming months :
- Clutch. I've got 138k on the factory clutch and with the additional power, it's lifespan has been cut significantly. The good news is I drive like an old woman and, so long as I'm babying it, the clutch should hold out. The big question becomes what clutch do I swap it with when the time comes? Part of me just wants to throw a factory clutch back in for the driveability. It won't perform perfectly but would "work" well. Yes, you need a new clutch. An OE clutch/flywheel might work well for a short period of time, but it will be prone to quick failure based on its new load. I'd recommend the UUC Stage 2 w/ Performance Organic Clutch, it's not cheap but it's completely proven to work under these conditions. Do it right the first time. http://store.uucmotorwerks.com/light...dels-p285.aspx
- Diff : Issue here is that if I put in an M3 diff, I believe I would have to swap out the entire subframe... and the problem with that results from the fact that I already did the subframe reinforcement kit. I believe that would make it a huge pain to swap out the diff. No, leave this stock.
- Pistons, rods, head gasket : I did the head gasket something like 15-20k miles ago but imagine it will also have a limited lifespan with boost pressures. Part of me wants to pull the motor when that time comes and rebuild the bottom with forged pistons, rings, and perhaps sleeve the motor (though I haven't really looked into this as much). Also, could add the head gasket that TT uses along with the longer head studs/bolts. No, don't touch anything until you have a problem. You know....don't fix it, if it's not broken.
Transmission : I hope the 5 speed holds out and harnesses the power.. if it becomes and issue, I think there are a couple other options I could look into. The only problem I face now is that, with a short second gear, I slam through 1-3 wayyyy too quickly. The amazing thing about the power is how smoothly it hits and, even while driving like miss daisy, how quickly I'm hitting 70-80 mph. One headache is that, at 80, I'm around 3500 rpms.. would prefer that to be a bit lower.Again, don't do anything, that 5 speed will hold all day long. Gearing, I wouldn't touch that either. Those RPM numbers sound real good, but hears a BMW gear calculator for you to play with. http://www.bokchoys.com/differential...calculator.htm