VEEDUBBED

Hello everyone,
Just a quick word to say that this is a great forum and has exellent tech. info.
Anyway,i need some advice,i don't actually own a Cosworth powered car but i do have my Vw corrado 16v turbo that i fitted with a compleat weber/iaw Pectal super 8 injector system robbed off a sierra cosworth that was mapped by GGR.
The engine runs fine but i have a few issues,the original Vw rev counter works but bounces about quite a bit,i've already fitted a small black noise suppressor off a 2.0 EFI sierra that i found in a mates car breaker and wired it onto the coil's output to the rev counter but it did'nt do squat.
The second problem is that when the engine's hot,sometimes the revs stick at (guess)4000rpm but if i press on the accelerator pedal a tad it usually brings down the rpm to normal levels.
If i disconnect the ISV the problem goes but then the motor stalls....
Lastly,the damm engine never starts off the key unless i touch the gas pedal,i'm thinking it may be the PF09 throttle switch messing around because the readout off my PLX R500 wideband shows that when i accelerate and then let the pedal return instead of going lean(cut off) it goes open circuit...
Any suggestions are most welcome.
Thanks.