sound like puff!! from my muffle when the engine shut off?
 

i have a civic z6 block y8 head, pistons 8.5:1 with t25 @ 10 psi, vafc, 450 cc injectors, fmic, 43psi fuel rail, 3degrees retard on camgear and 14 degrees at crankshaft pulley, runs great!! but sometimes this sounds come from the muffle when the turbo timer shut off the engine.
I have all this setup but where i live its hard to find a dyno tune, i live in Honduras Central America, so i set it up the vafc like you post in FAQ with some modifications seeing the a/f gauge and hearing the engine, like i said runs great, but this sounds i dont like it. any idea please let it know.