WRX runs fine from cold, but lack of boost if left for 5mins
 

I have just bought a 2003 impreza wrx, it is stage 1 re-mapped, straight through exhuast, walbro fuel pump, pro drive kit (or part of the prodrive kit)

The car runs fine from cold and seems to boost fine, but if I stop and switch off the engine for about 5 minutes, then switch the engine back on and drive it seems to lack boost, and it is very noticable in 2nd gear, after approx half a mile or driving it returns to normal again, this seems very odd to me and not knowing much about cars, I am puzzled.

I checked the oil level when the car was cold, and it was a little over the max line.

Any advice would be great, thanks.

Could be heat soak in the intercooler

What cooler are you running?

standard wrx intercooler