had a interesting talk with MPS at manufacturers cup race in valdosta. ga. sat. purchasing ignition kill box to finish up my air shifter project, question arose was i going to run nitrous. yeah, small shot. he recommended fuel kill, not ignition. why, so no pop or backfire during shifts? he answered no, so u dont spit shims and keepers. he developed the fuel kill for his personal use on his bike that has had problems spitting shims and keepers on the bottle with correct nitrous spring pressures.problem has never reoccured since fuel kill replacing ignition kill. ran nitrous window switch on both setups, so his problem was not from hitting rev limiter on juice. according to him, the "POP", or "BANG" we hear during shifts that results from reigniting a cylinder with fuel and nitrous, after first killing the spark, produces a powerful shock and sonic wave that impacts the valves operation and its vital components as in springs, retainers, keepers, and shims allowing things to be shocked out of thier necessary place, or spit out as we say. they claim this is not theory, but fact. told far less chance of spitting a shim or keeper with fuel kill on nitrous. just wanted to pass this along as members have experienced the same problems. for what its worth, im going fuel kill, he was very convincing and logical.