I read somewhere that cooling the fuel before it enters motor helps increase runtime and make motor run overall better is this true?I took my crash body and designed forced air ducts that blow directly on gas tank and directly on heat sink.....hopefuly not waist of time? i have pictures of it in the offroad section of the forums,,take a look and let me know.I think extending the fuel line will prolly help with cooling too..But i am new to rc so feed back is welcomed ty guys

Cooling the fuel will reduce it's volume, hence in theory yes you added a little more fuel to the tank than if it were warmer. It may also fail the test as the 16/25% rules are at 20 degrees Celsius.

While engine is running it will make little difference to performance as we restrict the fuel to acquire the fuel/air mixture. So it's not a matter of whether it cool or not as we can easily provide more fuel to the mix.

Cooling your fuel in humid climates will create a lot of condensation, best keep the cap on the bottle at all times.

You can marginally increase runtime - and by marginally I mean seconds per tank - by placing an exhaust gas cooler in the pressure line between the pipe and the tank, it helps lowering the fuel temperature in the tank by a few degrees.
The concept was originally applied by onroad guys who were struggling to finish qualifying sessions without refueling and needed those extra seconds of runtime.
Just search for it in the forum, you will find a lot of discussion about the subject, but the consensus appears to be that it's effect is little and even less felt in offroad racing