[s-cars] Boost cut-out?

[RM]

Hi! New here, just picked up a well taken care of 94 S4. Car was stock until
the other night when i swapped in an S6 ECM (same part # as the S4's) but it
had a TAP stage one chip. The performance change was noticable. It runs well
in all conditionsand i put about 500 miles on it since.  However just this
morning i was coming to work (very VERY cold morning) and after everything
was warmed up enough, i gave it some 'scoot' in second, took it to 6k rpm
and shifted to 3rd, only to have it cut out under partial throttle around
3-4k rpm, and then refire within a second or so. It continued to do this
until I finally pulled over, shut off the car, refired it and continued to
work. The problem didn't occur again. I'll be driving home tonight to see if
it cuts out again. The most recent thing i did was put a K&N air filter in
the other night but i have verified that all connections are secure. Any
thoughts? Can anyone give me a rough idea of what can cut-out the
fuel/injector pulse in these cars? Is there an overboost cut-out switch? Any
insight is appreciated!!

Rolf Mair