need help got 2 problems what is white smoke and a hung throttle

Ok dont know if these are together or not but what does white smoke mean? One other thing is the other night a truck was playing with me for the fun of it. So we did a little take off at the light up to 30mph and when I let off the gas it was just stuck there. So I hit the gas 3 times hard because I thought it got hung up or some thing nope.
SO I pull up to the light and the car is at 1500 RPM's So I put it into park and then it shoots up too 2000 Rpm's So I was like a dragster at the light. So I drove about 2 more miles like that till I got to my buddys house who has 65 mustang with 400hp out of his 302. So we just turned down the idle to about 800 RPM and we went on our way. later that night I was stopped at a red light and all of a sudden it just went down to 500.
I got a cam but damn that thing sounded like I had a big ass lift.