So I decided to swap coils and plugs. Afterwards my mpg dropped from around 19-20 to like 16. And at highway speeds it feels like it's misfiring. I did cheap out on the coils. Couldn't bear the thought of spending $300 on coils. Do you suppose I am paying for that now?

 

Why did you put new coils on it? Were you getting any misfires before?

 

It felt like it was misfiring.It lacked power for sure and it seemed like it was getting worse. My vagcom was being weird and not connecting to the car so I couldn't be sure. So I figured I'd swap them out. The car has 240000+ miles and they looked like they could be the originals so I assumed it couldn't hurt to put some fresh ones on. I did the coils first. Drove it to work and mileage plummeted. So the next day I did the plugs and that didn't effect anything. The coils were definitely old. The rubber lip at the end of them was very brittle. Not to say that that means they were bad.

I reinstalled my vagcom and got some codes
p0300 random multiple misfire
misfires on 4,5&6
p0102 mass air flow signal too low intermittent

 

Mass air flow sensor issues could cause misfires and gas milage issues. If the car doesn't know how much air it's getting, it doesn't know how much fuel to use and could be running rich using more fuel because it thinks it's getting more air.

 

Unplug the MAF and see if things get better. Really. If the MAF is "lying" to the ECU, mileage and performance will drop. The ECU will complain (Check Engine Light) but it can run the engine just fine with the O2 sensors.