marc those sadly are pants mate.
maybe go for traxxas' tuned pipe it is very good and give decent power increase as its been designed specifically for the 2.5 engine and works very well indeed...

Part #5487 Tuned pipe, Resonator, R.O.A.R. legal (aluminum, double-chamber) (fits Maxx vehicles with TRX Racing Engines)
Suggested retail price $55.00
RESONATOR™ DYNO-TUNED PERFORMANCE DUAL-CHAMBER PIPE FOR MAXX® TRUCKS: The Traxxas Resonator aluminum tuned pipe for Maxx trucks is specifically engineered to boost performance. It is the ultimate Maxx musclepipe! Traxxas Resonator aluminum tuned pipes are precision-engineered on the dyno to increase the power output of TRX® Racing Engines. The Resonator dual-chamber Maxx pipe (part #5487) provides an average peak torque increase of 16% resulting in brutal bottom end punch. A 10% increase in total power across the whole range provides smooth power delivery, perfect for the back yard or the race track. All Resonator pipes are fully polished to a beautiful mirror-chrome finish with a laser etched logo. Mounting hardware is included.
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