I could really use some helpful advice here....

I have a 2003 VW Jetta, 2.0 GL with about 150,000 miles on it. Recently, I noticed it running rough, and it gradually got worse over about 10 to 12 days. Finally, the check engine light kicked on and started blinking and it became so rough and I had so little power that it was no longer drivable. Checked the codes:

P0300- Random cylinder misfire detected
P0301- Cylinder 1 misfire condition
P0302- Cylinder 2 misfire condition
P0304- Cylinder 4 misfire condiiton

Here is a list of where I went with things:

1- Replaced spark plugs
2- Checked cables
3- Replaced ignition coil (there is no distributor)
4- Replaced crankshaft positioning sensor (a recommended fix at Autozone given the codes it was getting... although looking back, it doesn't make a ton of sense)
5- Checked the fuel pump
6- Replaced fuel filter

At this point, I was done pouring money into it and getting little results, so I took it to a place that specializes in foreign auto service. He gave me some ideas, but pointed to either a bad coil (which I had just replaced) or and issue with the ECM. *He also stated that the injectors were functioning properly*

I went back to Autozone and talked with someone that was rather knowledgeable (considerably more knowledgeable than the first guy) and he gave me another coil to try out. It didn't work. So the next place he went to was the ECM as well.

I was talking with another mechanic last night that also thinks it is the ECM, and mentioned something about how cylinders 1 and 4 fire and the same time, and 2 and 3 fire at the same time, and if I am getting a misfire on 1 and 4 that it probably has to do with the ECM and the way it is communicating with the ignition coil.

I just wanted to get some general opinions here before I go purchasing an ECM and taking the time to put it in only to be left with what essentially and non-functioning automobile again.

IS IT THE ECM???