I know its been discussed before on here and i've read the old threads, but mine seems to defy all other suggestions.

I have a 94 Z28 A4 with boltons, including longtubes, no egr or air pump, 255 walbro pump, adjustable fuel pressure regulator, new opti, etc.

i replaced the fuel pump because the car was refusing to start, turning over but not starting...still had the problem. i put the adjustable regulator on....still had the problem. the car will start no problem if its been running soon before, but always has a problem when its cold or been sitting for a little while. got a new starter and fuel filter in it too so...

i heard a clogged evap canister purge valve would do it, anyone else know if that could do it? tia...