I used this stuff and some carb cleaner on a boat with a ford 351 w V8 and a holley carb which would not hold idle last weekend:
Fuel Set Fuel Set Concentrated Fuel Conditioner - Only £17.95 - Force 4 Chandlery
It worked a treat. Saved there day. I have it in the back of the truck, if you want i can pop up to portisehead marina after work tonight, if you want to give it a go.
Regards
Ross