Ignition Mis-fire, lookin for a fix

[cobra0330]

when going up a incline the engine makes a real loud grind noise. originaly thought transfer or trans, ford told me it was ignition misfire, not enuff to make the truck stumble but enuff to hear it. (it gets very loud when runnin hot) they suggested 91 octane and hope it goes away . i am trying that and doing new plugs and wires, any body gone through this crap too?

 

[surf]

Got the same problem. Most people suggest it is caused by a vacuum leak, dirty MAF or bad intake manifold gasket.