Say what you will but the exhaust coolers do work. I put one to the test in my buggy using all the same equipment and the cooler being the only variable. I gained between 25-40 seconds runtime. For me this was the difference between being able to run a 10 minute qualifier without pitting. Your tune should not be affected. The only way the tune would be thrown off is if you somehow managed to develop an air leak through the cooler which is possible. Some of the coolers have threaded fittings which need to have the threads sealed to avoid any leaks. Some coolers like the one from RB are one piece so leaks are not an issue. As far as flaming in the pits a lot of it is in the tune, usually to rich on the bottom. Get the proper glow plug, get your tune right and then I would try the cooler out. A few seconds may not sound like much but in racing every little bit counts.