Mine seems to run good , a couple things to check are the exhaust valves and throttle cable tension. I added a defender intake and it hasn't missed a beat since. Make sure your intake is sealed up and together correctly. I have seen a few that aren't and those seem to bog on deep days. I have found that the leaks are at the top on the initial screen. When assembling that piece you need to disassemble the screen parts (3 screws per side) and reassemble when everything is in place. Some guys are just muscling them in to place and am finding the lower part of the intake screen has come apart. It is a little bugger to see so you need to check carefully. Mine is stock except for the defender.