Just purchased a 96 mustang gt off of a buddy of mine, it was running really rough got a good deal on it. Towed it home, dead battery. new battery its running really rough. said it wasn't running like that since he changed the lower intake manifold. he used an npi intake on npi heads so no issue there. i pulled the plugs and cylinder 4 and 8 boots were rusted on. bottom of plug 8 was rusted in cylinder. replace all plugs and wires with Motor craft replacement parts plugs are gapped to .54 its throwing codes p1443 p0401 p0303 p0306 and it has the same codes with pd after them. had a very small amount of 2 year old gas in it, ran cleaner through it with a fresh tank of chevron 91 octane. also seafoam'd with new gas, seamed to help the problem but its still misfiring and running really rough. plastic vacuum hose going to EGR is cracked and there is another plastic vacuum line that is cracked a well that will be getting replaced.