I have a built d16y8 that has been tuned on 22 pounds with a 3 inch down pipe and 2 1/4 inch exhaust. It ran good after the tune, later on down the road I changed the exhaust out for a 3 inch and ever since I changed it out in third gear at full boost it cuts in and out the boost fluctuates rapidly up and down once it's above 19 pounds. It is tuned with hondata s300 and boost is set by gear, 2nd gear is set at 19 pounds and runs smoothly through the rpms but when you get into 3rd it starts out smooth until you get into higher boost. Someone told me I may have to up the fuel pressure a bit, so I tried it and it seemed a little better but still cutting in and out. I know I'm going to have to get retuned probably but I just wanted to see what your opinions would be on this.