Early Wrx issue,
 

Question for the technical guys i'll start with the car,
1994 wrx (import) Td05 model.
Car is runing a Arc Tmic, Full 3inch decatted system using the twin pipe down pipe, Hks panel filter, and a Z4 ecu,new coil packs

Other than this as stock as they come. car is hitting 0.9-1bar off boost everytime, the car is in great shape and singing as it should, but seems to feel a tad flat between 4-5500rpm, feels like its not pulling enough, it comes on boost very well and spools as it should but high rpm feels weak, could this be the ecu pulling the timming back? no error codes are being shown,
any surrgestions what to check?
Any advice would be very appricated

Thanks Benji.

induction leak on discharge side of turbo? that black 90° bend on the top of the turbo is prone to going where the dump valve return joins it

all fine there, done all the normal hose checks and bossting fine, swapped maffs over and same outcome.

Overboosting perhaps in that region due to the decat and large 3" pipe. With ECU and 2 port pulling boost back. ?. Possibly combined with timing as you suggest as well.