Re: 2.0 Spider revving high!!
Common fault on the GTV/spider is the air inlet pipe splitting at the flexible section next to the throttle body. Check round the circumference of it to make sure it's not split down the joint. If it's split just gaffer tape the split up as a temporary repair (won't do it any harm) and get the part ordered up. Could be a good opportunity to fit an autodelta carbon intake, at £120 it's only about twice the price and includes a sport air filter (not used one myself though so not sure how good they are).
Could also be a bit of crud stuck in the butterfly in the throttle body, take the inlet pipe off and see if the butterfly is shutting correctly.
The fact it stops when you're braking could be to do with the way modern cars control fuel economy. Not sure if alfa's do this but I bet they do, the fuel is cut right down whilst braking or travelling downhill to reduce consumption and utilise momentum to turn the engine.
< Rob >
Spider 2.0 TS 1997
156 2.0 TS Selespeed 1999 (now sold)
147 2.0 TS Lusso 2002