On a mechanically supercharged engine, the supercharger's shaft speeds are directly proportional to engine RPM's. Thus, in a supercharged engine, " x" bar of manifold pressure will be achieved at the same motor RPM regardless of what transmission gear is engaged. This direct proportionality is due to the fact that the supercharger's shaft rotation is driven off the engine's crankshaft, or camshaft or other directly driven puley or gear. So, for example, if 10# boost is reached at 4000 motor RPM in 1st gear, then 10# will be attained likewise at 4000 RPM in all transmission gears.

On an exhaust driven turbine, or turbocharged car there does not exist a directly proportional relationship between manifold boost pressure and engine RPM's across the range of transmission gears.

Do a WOT pull in 4th gear starting at 3000 RPM and tell me at what RPM you see 20#(roughly 1.4BAR).

 

around 4000rpm

 

So, 20# @ 4000 in 4th gear is way too slow, way too late on a stock IX turbo setup. Ideally, you should be seeing that boost level somewhere around 3400 RPM.

We can try troubleshooting the issue with the factory ECU/BCS system. However, you had mentioned that you were thinking of installing an MBC. I prefer the MBC over the stock setup for troubleshooting wastegate control issues, and relative ease of determining wastegate spring pressure.

 

well ive ordered a hallman pro MBC along with injen intercooler piping kit and oil catch can