Most meth kits have a control system that senses low level of the fluid and this will trigger a fail-safe that will NOT alter the tune until the fluid level has been replenished.i dont know what kinda gains GT500s make on meth. but a safe shot of nitrous would be a better route mayb.
with meth you can turn up the timing quite a bit and you can run more boost and you have to be tuned... sure u knew that tho.. it prevents spark knock. ive seen more than one car blow up bc these guys were running their cars hard on an empty tank. if you do it you better get a 5 gallon tank, bc with the GT500 you will be running a pretty big nozzle. i think 12gph or so. do you research and know what your getting yourself into.