accompanied by sputtering and popping on the slowest end?
Sputtering and popping can be a fuel pump, it can also be several other things, spark plugs, sticking valves, valve lash out of adjustment, weak valve springs, TPS and more. Testing fuel pump is an easy sure fire way to eliminate that as the problem. Fuel pumps are also common issues. If it were me, I'd replace spark plugs unless it's been done recently or as recommended by frequency, read the old plugs just for good measure and if that didn't resolve the issue test the fuel pump before moving on. Do easy low/no cost things first, assure those things are proper then move on to other tests. As stated by RJ, throwing parts are it is an expensive, time consuming, inefficient, frustrating way to fix it, if you do fix it that way.