Concur with Doug and Greg, if all you changed was the air box before having problems go back to your last good run set-up, i.e. get the air box back on. If all else fails suggest getting it to Greg. I ran Rotax in RMAX and TAG configurations 2006-2008 and had great success with Shockwave built and tuned Rotax’s. Recommend Doug and or Greg, they are amoung the best in the country when it comes to great Rotax performance and reliability.