Code P301-304

[70GTORAG]

I have the same problem with my 99 passat 1.8T. The check engine light came on last week and the dealer pulled misfire codes, said it was likely a tank of bad gas. I ran the tank out and filled with new but the car still is not running right. Dealer pulled codes again and still had misfire codes P0301, 0302. There was also a P1300, and said fuel level too low. They suggested replacing the spark plugs, checking all vacuum hoses first, as they were the least expensive items. If after that it does not run right, it may be the MAF sensor.
From reading posts on misfire codes, there were several solutions/fixes that came up I would like more information on.

1. Is the MAF sensor in the airbox?
2. Does anybody know where wiring diagrams and vacuum line diagrams can be found online?
3. What is the ECT? Do you run test on it or is it just a replaceable item(cheap)?
4. The Power Output Stage test says to pull the engine side wire and put a test light on each terminal of the module as engine is cranked to see pulse. Which is the engine side? The wires enter a sleeve immediately and both run into a secondary sleeve at the rear of the engine, that lead to the ECM?
Short of these tests which I can perform, it will have to go to the dealer if nothing works. Anything else on the P1300 code Fuel Level Too Low or any other suggestions? Thanks.

[veedubmechanic]

1. yes have to remove the top portion of airbox to remove sensor
2. no
3. replace the ect (coolant temp sensor 10.00 in parts sensor/oring) look for previous posts on ect
4. if your engine is misfire on cyl 2 replace the pos "power output stage or ignition module" (reccomend one from a aftermarket parts warehouse and save 2-300.00 its on top of the intake box)

[70GTORAG]

Looked up posts on ECT, sounds like they are junk, just replace.
Will a faulty ECT cause the car to run slightly rough and store misfire codes P0301, p0302, and p1300(fuel level too low)?
I just topped up the coolant overflow reservoir over the weekend because it was below the low level line. Could this have any effect on the ECT or how it operates?