ok buddy, ill tell ya what i know. First off, the 535 weighs 3600 lbs stock. Shes got herself a fatt ass, but shes got some power in her legs. An IS is hard to find, so i would definitely get one. The BMP intake is iffy, as i had a powerflow intake and the k&n drop in just to settle the controversy. Right now im running the drop in, but if you can effectively shield the heat, go for the bmp. Taking out the hi beam for ram air has not been answered at all, despite the countless times ive asked on this board. The fives handle well, but mind you are not race cars. They have too much mass to effectively handle very nimbly, but i like the 5er because i love to drift, and the weight is perfect for me. I have an eat chip and that made the biggest difference. I just bought the triflo exhaust, and i love it, but i doubt it does to much. With all of my mods i estimate a 240hp/240tq. but the weight is a killer, and im trying to overcome it, but performance parts are few and expensive. If i were you i would wawit to a 540, and with around 150k, it should go for about 12k, depending on year. Good luck, and whatever you decide, your getting a bmw!
1990 535i 5 Speed +[E.A.T. chip/Powerflow intake/Tri-flo exhaust system/Strut Tower Bar/Smoked Signals/Pioneer Head Unit/Crossfire vr401 amp/12" Crossfire BMF sub/eyebrows/18" alpina replica rims]+
6 cylinders, 5 Speeds, 4 Doors, 3 Pedals, 2 Exhaust Pipes, 1 Ultimate Drving Machine