ciderhead

I am currently running a simota panel filter and 2.5'' hayward and scott system on my STI v7 . i replaced the centre cat with a 2.75'' miltek decat the car felt ok, more responsive, louder etc. One thing i did notice is that when on full throttle my boost gauge would go straight up to 20psi then drop off to a 15psi im just concerned because i cant remember it doing this when the oem cat was on.

Will removing the centre decat give you an increase in boost ?

Any surgestions would be great as i dont want to run it like this, if it can cause engine problems etc

Cheers