HELP: 98 RAM 1500 V8 Engine Trouble

I have a '98 RAM 1500 5.9L V8, and the engine hesitates when cruising at 45-50mph. It is fine under acceleration, and other speeds, but feels as though it is misfiring at 45-50mph. It isn't though.
It has had new leads, plugs, distr,...tested by the local garage who can't find anyything on the diagnostics.
I've used engine and injector cleaners but they don't help.
Any suggestions.
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Well, then its a figment of your imagination, cause it IS, or it ISNT.

Keep going...you just havent found the problem yet.

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TCF wrote:

On an older engine - especially four-bangers, a part throttle hesitation could quite often be traced to a bad (leaky diaphram) EGR valve.
Now that that's out of my system, does it also ping when this is happening?
Mark
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What I would sugest you do is check the compression. A lot of the late model motors have soft valves & will loose compression. It is also common for the cat converter to plug up
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