I asked about the bubble in the line and have been told it is normal. Seems odd to me but that is what I was told.

It seems they either run great or are problematic. I have one very similar to yours it will idle forever on the ground. Transition to full throttle is perfect. 15-20 mins of idle, full throttle and taxiing with no problems. But get in the air and go to idle for an approach and it goes dead stick.

It is not the tank since it was running fine with this setup previously. Changed the plug only 10 flights ago but will do it again just in case. But could a plug really cause this to happen?