Is it better for the boost to drop from 21 to 18 by redline??

 

its not better...if u get a boost controller...it should stay around 20-21 psi through redline

 

its not better, its just what happens when you get a factory turbocharged car, the factory tunes it to taper more then needed. dont know why, someone will probably chime in and say why.

 

emissions....and i think so morons dont blow their cars up.

 

bingo, so if someone runs regular 87 octane gas in the car at full boost it won't hole a piston. That's why the evos are so sloopy rich on the top end from the factory.

adding a mbc will add more air to provide a "more ideal" mixture at the top end, but will also reduce your margin of safety.

 

If you are tuned and on at least 91, it will be ok.