Originally Posted by GTTuner
My opinion is one of two things;
A torn inlet hose or FMIC piping leak, or the diverter valve is dumping massive amounts of air back into the loop. I know it dumps after the MAF, but when I was tuning my BOV I had the exact same condition when it was constantly on full recirc when cruising. Try disconnecting the vacuum line at your diverter valve and drive it to see if your surge is gone. Just don't get into any major boost with the valve disconnected.
You may want to try and clean the MAF if none of the above resolves it.
I mentioned in the original post that I noticed the symptom at constant throttle pressure, not really under acceleration (sometimes I notice a slight hesitation at the onset of acceleration). I'm still hitting my boost target and the valve seems to be releasing at the point it should be. Also, I seem to notice the most dramatic hesitation pulses, under very light throttle pressure or after I accelerate a little bit then back off the throttle and maintain constant pressure. Do you still think the above could be the case? I'm pretty confident all my hoses are well connected and that there are no tears, and that my FMIC piping is secure and not leaking. I've looked these over carefully, and so has my mechanic who is very familiar with Subarus and their modifications...not sure on the diverter valve disconnect though?....I suppose it could be doing what you mentioned. I could try that and make sure the MAF is very clean. Would you recommend I try this before logging my tuner data? Also, what would be the fix assuming disconnecting the vacuum line to the diverter valve seems to fix the problem?
Thanks for you input.