Yet another boost related question...

Got a Turbosmart boost tee from MSD - a nice little boost controller btw!
Plumbed it in between the comp housing and the actuator, got it to hit my desired 0.8bar of boost at around 3,300rpm. But by the time i get to 4,000-4,500rpm the boost drops to 0.5bar. Seems alot of peaking to me.

Any 1 had a similar problem, ive read maybe its a good idea to run the boost controller off the inlet manifold rather than the comp housing on the turbo.

Thanks in advance!