i have a 98 tracker 1.6 16v where i just rebuilt the engine, the problem is though it idles a lil ruff and after a minute or two it will loose rpm and go back and forth from about 1000 rpm down to 500 rpm for a lil bit till finally it will die like its getting smothered, if im driving down the road giving it gas it runs fine until i let off the gas then it starts lunging so im not sure if it would be a fuel filter or maybe a tps.