Vehicle Turbo Boost and Engine Sound Problem

hi everybody , sorry i was searched every where and unfortunately i didn’t find a good tutorial for it i need to make a turbo boost for my vehicle game and i want to make it something like motor storm in ps3 . i made it with this blueprints here but it’s not working as i want and every time i pushed my turbo bottom it makes my current speed double(or more it depend on the number you used in multiply ) and i can not hold down turbo bottom and it just worked one time if anyone knows the better way or a good solution i will be appreciate for that . i used the default advance vehicle and when my car speed is more than 90 km the engine sound will be vanished , if anyone knows any solution for this one too please tell me .

sorry for my bad English and thanks in advance .