Pulled codes on my code reader and that'* what I got. The live diagnostics show #6 cylinder weak at idle and normal when reved. Anybody know what this means. I'm still trying to figure out this scanner.

a pretty good guess would be a bad plug or a partially-clogged fuel injector.

naturally, it'* on a rear cylinder.

I'd do plugs and wires if they haven't been done recently. Makes a big difference.

The plug wires and plugs were just put in last week.

Code PO300 means that the computer has detected a misfire on this cylinder. I would change the plug and wire on this cylinder. If the code still repeats itself then change the coils around. After you changed the coils around and you still get a misfire on another cylinder bank then you know you have a faulty coil. I've been through this!!!

Will a coil pack from an 89 Bonneville interchange with the 94?

i dont think so... but if u need some coils i got some...

check out the for sale section in a couple minutes

Being that you recently changed the plugs and wires, swap the coils and look for the problem again. If it moved, then it'* the coil. If not, move swap wiire, and pull the plug. Maybe the plug is cracked.

Measure the resistance of each wire. It should be a natural increasing progression from 1, 3, 5 and 2, 4, 6. I'm betting you have a high resistance on #6 or a short to chassis ground through the insulation.

Yes, they should interchange, since a 91 3800 will take a 92 and up coil coilpack, and plug in the same.

I wouldn't use one. I believe some may be the old magnavox ignition, not a delco. Its not a great ignition system. Try one from a 92 and up.
I know I am looking for one myself.