1995 sunfire stumped

when I am at a stop I am getting like a misfire but it does not stall , or as some may say ruff idle. lights in dash will dime a bit when this happens ,and more so when I have the heat on high.now things I have done to this car,

put new injector in as other had a leak.

blower motor rely went ,and also come to find out that the motor had a dead spot in it to (real impressed with having to get under there again)

have changed the fuel filter

have put fuel injector cleaner in it

have checked for bad ground, dielectric grease on the batter posts

have had battery and alternator checked both are working fine .

system diagnostics done no falts detected.

new coil pacs later summer , but the ruff idle just started so don't think it has to do with that

do any of you have any ideas to what I can do next to figure this problem out ? thanks for all your help to this point :-)

Get a digital volt-ohm meter:

Set it on the AC voltage scale, and check the voltage at the battery. Anything more than .10 volts AC means you'll need diode in the alternator, or a rebuilt alternator.

I'd redo the grounds and check connectors.