I bought a 92 toyota 4x4 truck the prior owner had the original fuel injected engine and had approxamitly a 1985 carborated engine put in it.I drove it fof bout a year with no problems now when I can get it to run for about an hour justat an idle when it dies the gas in the bottom of the carb sound like it is boiling I have replaced fuel pump 2 carbs 1 intake each time I did that it ran for a couple days then the same thing happens. once it dies it will turn over like it going to start but that's it. sure could use some help