I have a 97 turbo civic with a d16y8
fully built t3/t4 on 20psi
Had 2 1/4” exhaust car did fantastic no boost cuts got to 20psi and stayed there

just recently got a 3” exhaust and now when ever I spool up to 20psi at around 5500-6000 rpm it basically starts to 2step and my rpm’s don’t get higher and my speed doesn’t get any faster. I’ve tried turning boost controller up and down and it does nothing. AFR’s are fine. Not sure what the issue is

 

What's your spark plugs gap set to?