[s-cars] Low RPM studdering miss

[Realcoast at aol.com]

Audifans,
My 93 S4, has a studdering miss
until about 3000+ rpm,
it seems likely electrical but occurred right after 
replacing the fuel pump.
I've gone through all standard tune up stuff,
Nothing showed in the codes,
Also it completely disappears without trace for
a half hour or so and just when I relax, bang its back.
Any suggestions would be much appreciated.
Thanks,
Dave Hallworth.
93 S4