Sounds like a MAP sensor problem mate. When they fail the ECU can't respond fast enough under load and sudden throttle openings as it's having to guess the air pressure which governs a lot of the running parameters.

I had a similar fault when I switched my 3i over to OFAC RS management and ballsed-up the wiring.

Like Tonto said, check the electrical connection to it, as well as all the vacuum pipes onto the inlet manifold.

Hope this helps.

Danny