Hey Scotty, my dad's 1999 Chevy Tahoe 5.7 v8 4 spd auto 180k miles has a engine power surging when interior accessories are used during acceleration, ac fan, power windows, radio and blinkers, it surges especially bad in sync with the blinkers but runs and accelerates great when everything shut off, no engine codes, I have replaced fuel pump and filter, battery, alternator, main battery ground cable and checked others, engine computer and I even had a macanic friend hook up his fancy $5k scan tool to see what he could find but nothing has helped, we have just about given up, what is your advice?
It's a wiring fault somewhere.
Try monitoring the voltage to your ignition module.
Definitely electrical as @mmj said. I'd start by load testing the alternator, even though you say it's relatively new.
