My engine has been running up to 240deg? It is also runing sluggish? I have a new enigine with AFR heads... it should be fast, but it seems sluggish? timming is at 6deg advanced, vacume is 16hg steady. No vacume leaks, no codes, cam was installed at TDC, good spark, firing order is correct, it runs fine, just seems sluggish? I have watched the prameters via Diacom and it seems fine, just sluggish? I have replaced both cats as well.....needless to say...I"m lost!

 

Since you already covered timing, exhaust blockage and vacuum leaks...

Running too lean
Water pump not working
Thermostat not working
Radiator not large enough to cool the engine or not enough air across the rad
Transmission too hot (oil through the cooler heats up the coolent)
Electric fans not coming on early enough or not at all
Heat range of spark plugs too high

 

Well, do your fans turn on? Everything in place (air damn, shroud)? Check your fuel pressure (seems like a recurring issue on the boards lately). Are the radiator hoses in good shape? Inspect your plugs. Just keep snooping around, I'm sure you'll find something amuck.