If you don't have a fuel pressure tester, you can get cheaply for your rig, it attaches at a threaded valve on the fuel injection rail. Hook it up and see what you got. You also don't want a bleed off when shut off engine. If can get a long enough hose you can tape to the windshield and watch while driving. If you do a pump, do the filter at same time. Can buy MAF cleaner and follow instructions to clean the MAF. Get carb cleaner and clean the throttle body bore. But you could still check all that and have clogged cats. Exhaust shops can check back pressure in the exhaust system for you. You also can put on a glove and have someone rev the engine while you are at the tailpipe and see if it has a nice strong flow of pressure coming out against your hand.
