My 07 TB, 5.3 V8, is having fuel pump issues. I replaced the original with an aftermarket pump. The engine seems to "buck" when it's cold, there are times when it will just crank as if it was out of gas, and it stalled on me while accelerating. Could this just be a bad pump or should I have replaced it with an OEM pump? Has anyone else dealt with these issues? I did a fuel pressure test and it showed 48 psi at ignition on, and 60 psi engine running at idle. Any help is appreciated.