I have now replaced the K-40 relay. Same problem!
Car runs 0-70 mph like a rocket. Second time it starts fast then boost drops to 0, it runs fast until I let off the pedal, then it is all slow from that point on.
Shut it off and let it sit for 10 minutes and it runs good again until I let off the pedal, then slow again. No boost or go fast.

Larry12