hi chubba, Nitro_Racer's advice works for my case too. i have GRP .12 mario rossi tuned engine too. it has a very good mileage but lack of punch generally.
if want to try nova gas cooler(in between tank and engine,more or less like a second fuel filter), u better tune yr engine slightly richer before u race tune it
the one u mention,between pipe and tank. i use Team C cooler.run time increase 5-15secs/tank, power wise no effect. once a month u need to use blower to clean the coolers internal.
hope this helps