about 10 years ago i bought my 1972 cb500-4 for 1000.00 cdn, it is in excellent shape and came with a helmet and riding jacket. it was my 1st bike and after taking it for a test ride i fell in love with it. its all original except for the motor which i had to replace after the main bearing went. i was able to find a replacement engine for 250.00 installed. it has an original 4 into 1 exhaust system. does the 4 into 1 exhaust give it more h.p. and if so how much? although i practice safe riding i have out of curiosity buried the needle at 120 m.p.h. once or twice very briefly as i am very much aware that traveling at those speeds can equal instant death should anything go awry. i would like to customize it for higher performance while keeping it as original looking as i can but dont know where to start. if anyone would be kind enough to give me some advise i would appreciate it very much.