2000 gmc truck 5.3 lt service engine soon

I have a service engine soon light that comes on and goes off, had it checked and was code 032 so i put plugs, wires, fuel pressure reg, and new fuel filter, the light comes on when i go above 70 miles an hour, last week it come on and flashed anywhere between 4 and 60 times seems to go back off after i drive it for a while at slower speeds. the light stayed on the whole time it would flash one 4 flashes the next 11 then 32 then 53 then 21 then 13 made no sence,

had it checked and was code 032

Was it P0320 or P0032?

not sure auto-zone said it was a engine missfire and I just needed to do a tune up.

So its a P0302? Which is a number two missfire. There are hundreds of trouble codes and each one is different. It important to have the right one as the direction it can lead may be opposite of the incorrect one you might have posted.

It might need intake gaskets,not a tune up and it is a common problem on the 4.8s,5.3s and 6.0s.The intake gaskets are made out of plastic,blowing out and sucking in air causing the missfire.Spray carb cleaner near the intake gasket area on both sides while running and if there is a change,needs intake gaskets.You do not drain any coolant out,no coolant passages going through the intake and the intake gaskets clip on the intake.Do not rely on anyone workin at AutoZone's advice,not certified and do not know what they are talking about

If it where a vacuum leak through the intake it should have flagged lean codes for both banks.

I have seen this happen even when the plugs have been changed,with bad intake gaskets.4.8s,5.3s and 6.0s do have vacuum.Plus it will show a whole bunch of fake codes.I have seen one Chevy truck do this with other false codes.