Big difference. I think the later wrx's use a TD04L (can someone confirm that?) which is bigger then the gc8 TD04, but you will still notice a big difference (least i did), it will come on harder and for longer. You will notice it doesnt run out of puff near the 5k mark but instead go for the redline!

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