If you have money to blow while still being responsible it isn't hard to get nice gains out of any motor. But not everyone can afford a new bottom end, machining, sleeving, head components, and a beefy turbo system.

All I told him was that the z6 is weak stock, and if he wanted to get some power out of it, he'd be spending more than a b16 swap. He never said he wanted to build anything, he just wanted to have fun with it.

^^^bingo. I never even consider a a2 motor for the sake of it being obd2 and having to convert back to obd1 to tune.