hopefull an expert can shed some light on this, the car an EBC electronic boost controller running 1.2 bar, the car accelerates fine great boost curve etc, spools up at under 3k revs full boost at 3.5k
The problem is the car accelerates fine but it feels like it's holding back and the boosting is a bit wavy, it's very subtle not "on off" the contrller is holding 1.2 bar with no problems, I have a loose heat shield on the up pipe im wondeirng if this could cause the ignition to be retarded due to the rattling and the \|ECU getting confused maybe!

 

Check the smaller boost/vacuum pipes coming off your inlet manifold for splits. I'm defo no expert but i had one split coming off the top od the manifold which caused my car to 'hold back' when accelerating hard.

 

This could also be a totally different issue to boost, it could be one of your coilpacks is up the spout or your plugs!