Truck had been running fine, has been seting in my garage for 2 months with a start up now and then. Took it for a drive and i could not get it up past 2000 rpms. no check engine light, but the codes read p0300 and p03001 and p03006 so I replaced plugs wires cap and rotor and TPS and it still gives me the same codes the the cylinders changed from the first time i checked the codes.
240,000 miles on it, but has had oil changed every 3000 miles or so.will barley idle and can rap it up past 3000 at best and lots of missing.
vacuum hoses look good but could of missed one.

Please advise
Buster

 

How's your fuel? Pressure? Volume good? Contaminated?

 

Pull the front O2 sensor out of the exhaust, see if it runs any better.

 

Was your plenum gasket ever replaced?