Where are the spark plugs

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It doesn't seem to me it is a routing problem. I think you have a spark plug wire leak instead.Replace wires.

You didn't say what size engine, but I think all of the 2005 models have direct ignition, which means each cylinder has a coil on top of the spark plug.
Are you talking about that ?

It takes fuel, air, spark, compression of at least 80 psi to fire a cylinder, your missing one, how did you check that cylinder for fuel?

Do you have the proper tools to do it?

All you need is a socket wrench and the correct socket, plus new spark plugs. Get a decent wrench (about $15) and the proper socket. (about $3)

Pull off ONE of the spark plug wires [ONE AT A TIME so you don't get them mixed up].
Take the old spark plug out with the socket wrench. Screw the new plug in and tighten securely. Replace plug wire. Make sure it "snaps" down securely over the end of the plug.
Do the next plug until all are done.

If you can't figure out where the spark plug wires are at then I really can't help you..
Go to the library. The library has Chilton Auto books with pictures to show you how to do it. You will not be able to take these books out of the library but you can make copies, so bring some change.

autozone will scan for free

Seems like this car have the same symptom wherever it is, I have this trouble as well, I did the tune up, injection cleaning, change spark plugs and spark plugs wires, change the air filter, change the engine mounting but still the same trouble :(

i had that with my mk3 golf..and i done everything i could then finally i changed the ecu relay fuse. that solved it completely. they are cheap to buy from vw..like £15ish. hope this helps

the hummer h1 have an diesel engine , i think about you never find the spark plugs

Make sure the part store gave you the correct plugs and wires. Consult a third source for a firing order.