had my focs rs since last april no probs really current mods include

Bluefinn
K&N Gen 2
Bailey DV36Si
Full Miltec s/s exhaust and decat
Ford Motorsport manifold
full RR tune

Its been behaving oddly the last couple of days, today especially so, as i put my foos down it boosts then on changing gear i get like what feels like serious turbo lag, then a backfire pop out of the exhaust.

Im wondering if its the dump valve as this is known to cause problems with the rs. Has any1 got any ideas? Do you have to keep tuning the car every so often to keep it running properly?


Any info or advice appreciated as im an amateur when it comes to mechanics!