Ok well you have a hot side and cool side to your cooler system. Hot side can stay the way it is, uncovered, but the cool side can be coated in a HPC i believe its called. Some sort of coating that retains it coolness whilst going into you intake. The difference between S/S and ally i think is that S/S will give off more heat through its material then alluminium will. SO if S/S gives off more heat through its pipe work to the hotside of the intercooler, it will get cooler air on the outgoing side as the overall temp of the air going into the hot side is marginally cooler due to heat loss.

Therefore the outgoing temp is cooler, making your car run harder, and thus is a performance difference. Feel free to correct me but i THINK this is the case. ALso look at turning your cooler upside down. Aparently you can lose up to 80cm of pipe work!

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Honda Hannspree Edition CBR 600 RR - SOLD
Yamaha FZ1N - Purchased