Put new fox plug in today without idle bar, and used 10% nitro fuel. Engine starts much easier but wont idle quite as low. Smoother transition from idle to full power also. I think in weather around the 30s its a good thing but not in the summer. As for the compression increase from the bar, it does make sense thats alot of difference in such a small space. I included a pic so you can see what they look like.