Re: Spider Problem.
Do a quick search on MAF, we traded up from an MGF to a Spider and had the same issue (albeit that the light wasn't on) - the performance sucked... searching on here we we pretty sure it was the MAF so we ordered a new one. In the meantime we drove it around with the MAF unplugged - and it works a little better that way, but unfortunately the management light comes on and power is down on a fully functioning one.
When we put the new MAF on the light went out (it doesn't always so you may need to reset the ECU - again look on here for instructions) or you can go to a specialist and get it reset (costs up to £60 depending on where you go).
have a quick look - i suspect your MAF may be disconnected (and possibly broken). If you plug it back in and the performance goes down (can't rev over 3400) then that's probably the problem.
They're reasonably cheap (at £120) and there are some instructions on how to clean the broken ones (on here) but that didn't work for us.. Budget around £120 for a new one.
With the new MAf on the car is a bit quicker - but it's still slower than the MGF.... actually I am not sure that's true - it just feels slower.. It's more Grand Tourer than sportscar, i suspect it's partly down to the Alfa being more 'refined' and 'grown up'.