Ray:
I too lost my kitty, Cummins runs 100-150 deg. cooler EGT. The cat was clogged so much that I could barely see light through it. I drove out to Pheonix last weekend and got 18. 6 mpg on two lane mountain roads, returned via I-10 with the cruise set at 75 mph and got 20. 4 mpg. I don't miss the cat, or the muffler.
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'97 5-speed, 4x4, 4:10 lsd, Horton, GearVendors, Ranchos, 255/85 Dunlop Radial Rovers, Ranch Hand rear and TJM front bumpers, 6 CD Changer, no Cat, no muffler, EGT/Boost gauges, Bright Box. 19. 5 mpg bobtail, 14 mpg towing 25' TT.