ECM gone BAD? a little suspect!

[ITZA72]

fellow members - my 87 EFI's been in for an overhaul - (spun a bearing but otherwise ran great) however the mechanic just hasn't been able to get her to stay running once put in gear (auto). After nearly two weeks of chasing vac lines, wires etc he believes the ECM went bad? My question - how could this have happened? shorted, pinched or ?? wiring ?? Gone from good to bad while sitting or perhaps they hooked something back up wrong?

Before I get stupid with the shop owner I thought I'd throw this out at at you all. Thoughts . . .?

Bless the troops deployed and supporting our great nation all over the world!