A while back there was a thread on 2.5L stroker upgrades and I was in the middle of mine, because of bad #2 main bearing. I finally got my car back from my mechanic and wanted to post the results. What I did was basically a 2.4L upgrade.
I purchased the EVO crank from Turner, ordered JE Pistons in the stock size bores (11:1 comp) and slightly honed the cylinders, lightend wrist pins, stock connecting rods, EVO Flywheel, EVO II intake cam was moved to the exhaust side, EVOIII intake cam, EVOII exhaust cam gear. The top-end was otherwise stock. While I was in there I installed E34 M5 guibo, rebuilt driveshaft, stiffer engine mounts, E36 cam chain tensioner and jet hot coated the stock headers.
The car had more torque and feels as if this is how the engine should have been made. Usable power builds right after 2k rpm now as opposed to 3400 rpm stock. The extra torque makes the car much more fun and first gear winds out really fast now. I'm still breaking in the engine and I haven't had it above 4500 rpm. I'm really happy with my so called 2.4L engine. I can't wait to take it to 6500 rpm or so. I'm not going to redline with the lumpier cams just to be safe. Maybe after I get better valve springs when I do the top-end I'll see some time at redline.
I want to thank all the guys for the great information (Kareem E36 Tensioner and Gustave for his upgrade tips on his website). Couldn't have done it without the little trick mods that made the difference.
'89 M3 AlpineweissII (it's alive!)