problems wanting to start up. like its not getting fuel to turn over on 1990 Nissan Maxima

first replaced fuel filter which worked it would start and run, but only lasted a couple of days. Then back to the same, and was looking to find another filter that we could of missed and found one of the egr vacum line was jammed full of carbon so cleared a few hoses and egr sylnoid valve and tryed to starting to blow the rest clear and found that if we pluged one of the vacume lines it would start and run again but the moment you realease the hose the car would bog down sputter and die so it was a temp fix that lasted a week or sothen back to not startin so this time if was just the oppisite. if you pluged it hose it would sputter and die live open it would start and run. now its doin it again and the hoses clogged with carbon. we feel like we really have just been getting lucky and all but now its back to the same and still really no real answer or solution to the problem. Any ideas would be very helpful thanks.

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2 answers
Have it scanned.
seek diag and est