87 Nissan Trucks Stalling Problem

I have an 87 Nissan hardbody truck, 2wd, with the SE-V6 engine. It is in excellent shape however I have an intermittent problem that recently started. While driving at speed it will just quit, if I press on the gas right then it starts right back up. Sometimes it continues to do this quit / start routine for a while, others it does it once or twice and then is fine. If it is happening at a stop light I have to brake and pump the gas and do the clutch at the same time. Starting from a stop when this is occuring is difficult as it quits hard, hit the gas and it goes, quits, hit the gas and so on. It does not seem to be temperature related as it has happend in the morning and evening on way home from work.

Since this started I have put in 2 new fuel filters, changed out the fuel lines, run cleaner through the gas. It all started right after puting in new spark plugs and replacing a number of the old rubber vacum lines. Any ideas would be GREATLY appreciated.

This truck has 225k miles, never wrecked, always garaged and carefully maintained. It even has no paint fade at all and I live in Phoenix.