how to fix the codes P0300 thru P0306

It's highly unlikely all those plugs have failed. I'm guessing you have the V6 based on the P0305 code, but the 4 cylinder engines have a lot of problems with the ignition coils, but it's unlikely 5 of those would fail at the same time too. This really requires performing some tests, monitoring the ignition system, checking engine compression, fuel pressure and intake leaks. You can read about these codes here for more info: http://repairpal.com/OBD-Code-P0300

Its the coil. A quick way to test is: turn the car on, spray coil with water. If the car runs worse you need a new coil. Same thing happened to me. Changed all the spark plugs and all the cables, then ran the spray bottle test and found out it was the coil.

Hi I`m Jerry Bryant and I am a true journeymen technician 36 years multiple automotive manufacturers foreign and domestic gas diesel, and owner operator of three independent repair facilities. So you know I`m not guessing. Ok you have a 2001 VW JETTA VR6 multi engine misfires, if you start engine in a dark place hood open viewing the coil pack you will observe sparks from every direction because of insulator decomposition witch believe it or not is very common as there is a TSB (technical service bulletin) from VW MNFCT. my professional advice is replace coil pack wires and plugs. Reason being when plugs are not firing correctly with the turbulence in the cylinder they may tend to misfire even after the correct repair was performed. I am assuming the vehicle ran great after the spark plugs were replaced because of an underlying problem. I think you will be very happy with your findings. Also it is recommended to install original parts from manufacturer exp. (VW) because of wire resistance and KV out put, parts store coil packs tend to fail prematurely. Thanks Dean