Cotterrell

I have a 94 v2 impreza wrx sti I have just had the engine built 2.1 stroker, v3 wrx sti heads and inlet manilfold, td06 20g turbo, rcm fuel pump, alkatec/simtec ecu, rcm gt spec headers, 440cc injectors. Now I took the car off the road around 8 months ago because the bottom end had started to knock so took the engine out and took it to well known Subaru specialist and he re-built it for me it's a closed deck blog had the block machined to rear thrust and other machine work for bigger crank etc Got some v3 sti heads and inlet had heads rebuilt anyway you get the picture, now I got the engine back put it in fired it up all was ok sounded a little bit rough but I thought just the fuel gone a bit stale so filled it up with v power anyway did a few miles in it that night and was running nice had the occasional splutter but again thought that was bad fuel, the next day it started getting worse spluttering, bad idle, popping out of exhaust and out of air filter but then suddenly it would be ok for for a couple of miles then start doing it again and now it's got to the point we're it's like it all the time so I haven't been driving it as I don't want to damage the engine, I took the plugs out this evening and they looked ok were quite black and sooty though, but all the same, i tried changing the fuel pressure regulator this evening and swapped the fuel pump to the OE one and they made no difference at all. Obviously it had new plugs and filters when I put the engine in