99 chev Tahoe 5.7 engine 4WD problem

Tahoe was stumbling on take off and/or at
red light, put in neutral ran fine or speed up
ran fine. My husband replaced mass
airflow & fuel injectors. Now turns over will
not run, in the past he had to get a bypass
module due to passlock fail. Took to dealer
for that no part available, so we got a
bypass module and installed and untill we
started having the stumbling issues was
running fine.