2000 Yukon, random stalling & starting problems

After stalling and not re-starting, a mechanic recommended replacing the fuel pump and module, which we did. Worked fine for a few days and now randomly stalls and sometimes won't start after previous use. Vehicle has only 80,000 miles but is now unreliable as family transportation. A trusted mechanic has run computer diagnostics, checked the fuel system, checked the ignition system, etc. Bottom line, he can't find anything wrong and can't think of any obvious issues. Bet I'm not the only one with this problem, any suggestions? At my wits end!

Welcome to AF. So when it won't start does it have sufficient spark and will it it start if carb cleaner is sprayed into the intake, these are basic diagnostic steps.