Definitely try the fuel filter and check NO LOAD max rpm. You will need some kind of tachometer, either a factory or aftermarket gauge, a photo tach that reflects light off reflective tape applied to the balancer or a stroboscopic tach where you "freeze" the balancer with the light and take the reading this occured at. It should be 2825 to 2925. You can check it with the accelerator pedal and by moving the throttle lever on the pump to the max fuel position to see if there is a difference-if so it means the linkage is at fault. The lever should contact the full speed screw when the accelerator is fully depressed. If the rpm does not meet the specification with the lever contacting the screw it means the fuel pump itself may be at fault. The service manual says to replace the fuel pump under these conditions. If the rpm checks out under no load but is weak at full load then fuel restriction, timing or air leaks may be the cause.
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'93 W350 Club Cab, Bright White, 5 sp. , 132K, Factory Options: LE, 4. 10 Limited Slip, 7600 lb. rear springs, tachometer, front stabilizer bar. Mods: Banks stinger plus, Linex bedliner, 25,000 lb gooseneck ball, 10,000 lb receiver, Tekonsha brake controller, POWER WAGON injectors-WAY faster than stock!.
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