On a completely stock Evo and only with a boost controler. I think You can take it up to 18psi with not much. Any higher you will experiance fuel cut.. That's when the car start jerking at high rpm's which is bad. But anyway the stock ECU won't let you do that to it so you will be safe..
A friend of mine got a very heavely moded Evo 7 and he can get it upto 30psi which is 2.1. So Espen 2.1 over here any body higher
by the way you got pm.. corvette97