do these help acceleration in a 670 mxz? son wants his sled faster. or is my money better spent other mods. i`m going to d0 the 501 rotary valve and head cut. and short boots . thanks for any help

I,ve heard good things about them. Goodwin Performance also has a composite arm that weighs 31.5 grams. I wish I could find a used set. New ones are too much coin.