I installed a new alternator on my 86 300zx na. the car ran good that nite but the next day the idle was rough and there was heistation at cruising speed. i had the alt checked, checked the voltage and it was spitting out 14.0 and 14.1 volts. i ran the diags and threw a 23. so i changed the tps and the fpr for good measure. thought i had the problem solved and did for about 10 miles. car started cutting out again but after sitting an hour, it ran pretty good, only one hesitation. i thought i might have water in the gas tank so i pour an additive in. I dont think i have a fuel pump problem or a maf problem, i can do 65, 75, etc in the car. im thinking i have an fuel/air. any ideas?