I have an old Nissan and seems to have a carb. problem runs good at high speed but surges at slow speed I am guessing gummed up carb. does anyone know any good additive that might clear it out, are is a carb. job the only alternative.

I would run some SeaFoam through..you should post this in the 'Boats and Motor section' also..

If it doesn't show improvement within a couple of tanks using Sea Foam, you need to clean the carb. You're running lean at idle and you run the risk of burning pistons with a constant lean fuel mixture.

Where can I find seafoam I don't recall seeing it anywhere

O'Reilly --Advance..AutoZone or most any bigger auto parts chain store has it..

Cheaper at northern tool.