Kombi is a '77 dual cab 2L, I had it tuned and carbs rejetted and cleaned less than a month ago. It's run great since except for yesterday. I put fuel in before going for a cruise and that's when the problems started. It'll run for a minute or so just like normal but then start to splutter, won't rev properly and loses power, if I pull over for a couple minutes and let it idle then start off again it's fine for another minute but then plays up again. It's also backfiring and popping a little on deceleration which it wasn't doing before.
I've changed the fuel filter thinking it was dirty fuel but it made no difference, the old filter was a little dirty but not much and the new filter is still clean. I've pulled the plugs and regapped and cleaned them. I've checked for any loose hoses, wires or air leaks. It's running an electronic ignition module to replace points, extractors and electric fuel pump but otherwise stock.
Any ideas? Any help would be appreciated, it's really shitting me at the moment.

cheers, Scotty

try changing back to a points system to see if the electronic ignition isnt stuffed

^^ yep or check for a plugged idle jet

Thanks fellas.

Seems the problem is due to the cheap electronic ignition kit I had fitted. Thanks to Steve from Kombi Rescue for the help.