06 BRM Misfire???

I have a 2006 Jetta TDi. It has an odd problem at times. It only does it when we change elevation (We live at 10,000 foot). Over the weekend we went to a buddy's house and while cruising down the highway (We were at roughly 7-8000') there was a quick (I assume) misfire. It basically just went bump bump bump and then kept cruising. The wife told me today she was driving and it did it a few times on her today. It's always just a 3 studder or misfire. No codes are being thrown and the car runs fine other than the occasional "mis".

The camshaft was just replaced and has less than 1000 miles on it! It has done this before the camshaft was replaced but it's been a while. It really seems it only does it when we change altitude! Any ideas on what to check or what it could be? Thanks a bunch!

Anyone???

I had something like this and it ended up being the injector harness. It seemed like it only did it under load but in fact it was just random which threw off my troubleshooting.