I recently purchased and installed GT-Spec headers and up-pipe kit. Since then I've noticed that my boost spikes to the set pressure (16psi), then goes down to 14psi at around 5500 RPM. Prior to the headers I had an HKS 3" downpipe and cat-back installed and never had a problem holding boost at 16. I have an HKS EVC IV controlling my boost... Anyone have anything to comment on what the problem could be? ECU?

P.S. What is "Re-flashing your ECU?"....

 

Change your downpipe. The fact that HKS isn't a bell mouth is a huge problem, and that's where most of your boost drop off problem occurs from. There are many better, bell mouth, pipes available such as Groupe-S, Perrin, PDE, ScoobySport, Grahm Goode, etc.

As for re-flashing, IMO it's the best engine management you can get. The program is called ECUtek, and it reprograms your factory E.C.U. for the mods you have. It also eliminates the need for a boost controller, as it maps it out for you. Best part is, it's undetectable by SOA.