I posted a similar query about 2-3 months ago. Similar to you I can from a big engined turbo beast to the refined handling of the 2.0 spider. Mine is a 2001 model, but apparently it is a problem on the twinspark engine. i have solved my the problem, but it's gonna cost.
Firstly do not use a high pressure jet wash. The alfa engine is prone to collecting moisture around the plugs. A good dose of WD40 helps to eliminate this, but stick to the bucket and sponge.
I've had my chip mapped. The accelerator is e-gas, ie. no throttle wire, it's all done electrically. I now touch the pedal and away she goes. It has also had the rev limit moved to 7500rpm so you get the full rev potential from the car. It's added an extra 10bhp. I've also had a carbon air intake put on and changed the standard exhaust to a dual twin. She now goes like the clappers and sounds even better !! Total 180 bhp, but cost me a grand to do. But what a car I've got now, handles and picks up superbly.