HELP! "Cylinder missing" in our 2002 Grand Cherokee

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We took our 2002 Jeep in for the 30,000 mile service 2 weeks ago. When I checked the truck in, the service person asked if I wanted the fuel injectors cleaned along with the tune-up. They said it was recommended by the service dept, so I said fine. Since this service, when the truck is in cruise and goes uphill, it takes off like a horse out of a starting gate! Very scary! It was also running very rough, my husbands technical term is it "hiccups"! So back to the dealer...They said all their computer tests showed absolutely nothing wrong with the engine. But it is obvious there is something wrong and they do agree with that, the service manager said it sounds like a "cylinder is missing". When you count it, you can hear it missing. They got in touch with Chrysler who said it must be the computer since nothing shows up as wrong, so they replaced that today with the same results. Jeep checks out fine on computer but is still "missing". Does anyone have any ideas as to what is going on with this truck? Has this happened to anyone else? Any idea how to fix this problem, the dealer is at a loss and said "Chrysler is scratching their heads over this one too!" It has been almost a week, how long do I give it before I ask for the regional manager? By the way,they have no loaner vehicles at this dealership so this is not exactly convenient! Any help and/or suggestions would be most appreciated! TIA

[bobby95]

Have they done a compression check?

[GrCherokee]

It could be your fuel pump lost the pressure.
BR,
Arkadiy