My friend has an 05 gsr and just had a HKS evc put on as well as a tune. Since that date everytime he goes past 4000 either his blow off flutters or something. it sounds like it is continiously going off under any throttle above 4000 in every gear. The blow off is an aps but we have also tried two different stock mr blow off.

This is really killing the power of the car so if anyone has and similar experiences, questions or answers please help out.

 

HKS has really nice BC. Make sure the lines are connected as they need to be per EVC instructions. Also there is a switch on the back of the unit, try experimenting with that (its for Internal vs External WG)

Good luck.