Plz help about GT4 Rear Diff, Can a different rear diff reduce Turbo boost? Options

[Rav4Race]

Hi guys/Gals...

Am facing a problem:( I had an engine swap, from in my 2000 model Rav4 which i fitted with a GT4 ST205 engine.
Am getting a low turbo boost:( My turbo is

not boosting more than 0.4 bar:(

Do u think its because i havent changed the rear diff? Am still running with my 1AZ-FSE rear diff.

but can a rear diff reduce the turbo boost??

plz help and thnx again bros:)

[Rav4Race]

Hi am back again. Well ive managed to install the rear diff of the GT4 and i can feel that my car is running smoother. But the boost problem as expected is still persisting:( There are no error codes and ive changed my fuel pump to a walbro 255 lph and added a sard fuel regulator.

Can anyone tell me how much psi i should be running of fuel pressure????

I think the boost problem is because of some kind of leaks that i cant find:( The wastegate did not stuck open. Am boosting like 6 psi actually:(
Does anyone have some kind of tests to check where r the leaks??

plz help