2000 Pontiac Bonneville Issues

Engine: 3.8l GM Series 2 3800 NA

Issues: Tachometer occasionally drops to 0, engine keeps running.
Stalled twice since last Sunday (10 days).
Wouldn’t start after sitting for 2 hours yesterday; waited 10 minutes, tried again, waited 15 seconds, fired right up.
When it died this morning, it wouldn’t​ start right away, but it sounded like it was almost there; after pushing it to the side of the road, it started right up.
2-3 weeks ago I was pulling into the garage and all the lights turned off for a second and the engine stuttered, but it caught again and kept running.

I’m thinking it’s an issue with the ECU.
I’ve already checked battery cables, they are tight.
Recently did plugs and wires, ran some fuel system cleaner through it.
Note: I don’t give a crap about this car. If it’s toast then oh well, doesn’t bother me at all.
Your thoughts would be appreciated.