MK2 GTI Hesitation

[CTE]

Hi There, I do not know if anyone can help.

I have a MK2 GTI with a dealer fitted "Plus pack" (1986 by GTI Engineering), which is basically a higher lift cam and a header manifold. The engine runs the original Bosch K jetronic fuel injection, and infact the car is totally original.

Whilst driving at constant (light) throttle, the engine continually hesitates (especially below 3500rpm), but if you put it under load, even a small amount, it smooths out. It does seem to pink a little too much when under full load and higher revs. It has also developed a habit of backfiring in the exhaust more recently.
This led me to believe it was running too rich, and therefore I went to a local garage at the weekend, who put in on their gas analyser, and we tweaked the mixture screw so all looked fine. I test drove the car, and it appeared to be better than ever, running smoothly, and no back firing. However, after 200 miles since then, it is a bad now as ever.

Any ideas?? Yes I have contacted GTI engineering, or whatever they call themselves these days, and perhaps not surprisingly in this money orientated world, they were not interested, and could not even remeber the work they had done. I do not know how many "Plus packs" they would have supplied, but it must have been in the hundreds?

[lotisi]

Sounds like the air flow meter requires adjusting, it's explained fairly clearly in the Haynes book of lies but beware that after adjustment the mixture will need resetting. Whilst your at it check for airleaks and make sure the advance diaphram is working on the dizzy.