hi everyone just bought rx7 2 weeks ago and i'm noticing a weird boost pattern in 3rd gear only, all other gears are ok. when i shift into 3rd @wot i have full boost at 10 psi @the transition it drops to 8psi then i'm only getting 5psi.. I know the pattern should be 10-8-10 My question is what could be the possible causes of this.

my mods are:
racing beat cat back
apexi intake
boost gauge
new engine(core)
one new turbo
one rebuilt turbo

when engine was did not have a hose job could this be the cause?

thanks in advance,
mike