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Hello All,

My VG30E is missing / stumbling at all ranges (smooths out a little at higher revs). I've done:

new cap, rotor, plugs, wires, fuel filter

coil resistance good

get spark at every wire boot

checked EGR, PCV valves

only trouble code is a 34- knock sensor

My neighbor held a dollar bill to the exhaust pipe at idle, and it intermittently sucked the bill against the pipe. He said that indicated a sucking valve. I put Marvel Mystery Oil in crankcase and B12 Chemtool in the gas, and drove it for a week with no results.

I've since checked compression on cylinders, which averaged 135psi. The plugs all looked similar after 120 miles except for #4, which had clean metal, with only some scorching on the ceramic insulator.

1.) Could a misfiring cylinder create enough vacuum in the exhaust to suck a dollar bill up against the pipe?

2.) Would I get good compression if a valve was burnt/stuck open?

3.) Could I have a clogged/defective fuel injector?

4.) Is there an easy yet definitive way to test a fuel injector? (#4 is buried under the intake plenum)

Thanks for any help or answers,
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