Boost bog down

I've recently been experiencing some boost problems on my adub. It periodically seems to bog down when the S/C engages, sometimes it picks up when the revs do and other times it has almost lost all acceleration at all until I ease off so the S/C disengages. Then again some days it runs incredibly well and is really responsive as it should be. It doesnt seem to be losing any boost so I'm wondering if it is fuel delivery related. Could it be AFM or TPS related issue? Any help is appreciated.
 
Cheers