Andre writes:

<< Low fuel boost makes engine run rough>>

Any chance the fuel pump is sucking air past its shaft seal when it is running? This could be a symptom of  worn pump bearings or seal. 

A simple test would be to remove the cowl and disconnect the fuel line from the engine and put it into a clean bucket (extend the hose as needed). Have an assistant and fire extinguisher handy. Turn on the fuel pump and, after the flow is established submerge the end of the hose to check for bubbles. 

While you are at it, time the flow to verify sufficient GPMs.

You should also verify that the fuel pump vent line is connected to the outside vent. Having cabin pressure at this port would make the problem worse. With the setup above and the pump running, blow a little air into the vent and see if that makes bubbles.

Perhaps not savvy or wise, but something to test.

Regards
Brent Regan