Originally Posted by Brandon Melton

for now don't mind all the people telling you it's an air leak, no sense in dissassembling things when it's most likely what Joe said the LSN is just too rich and the idle gap too large. Although the only thing I would stay away from that he said is adjusting the MRN. Very few people are good enough tuners to utilize the mid range, just leave it where the factory had it (flush around 2:00). You can most likely correct your issue with just the idle screw and LSN. I would say 50% of the people at the track running nitro have a double idle of some sort, especially on Vspecs because they still get around the track just fine with a rich LSN. Some engines with a rich LSN just don't run good an force you to find an optimal tun, Vspecs will stay running even when they are way off, which is why some people love them.

Just a heads up though, if the LSN is rich enough to cause this problem, your HSN may be too lean once you get it fixed, so re-check that. If the LSN and idle adjustments don't fix it, then look possibly into gaskets, and areas that could cause a leak, sure it's possible just a lot easier to start with just one screwdriver.