ok well today i got plates on my car and everything and when i took it out for a test drive it as heated up and everything the car wouldn't go past 2,500rpms when it reached that the car wud buck and seem like it was redlining, this doesn't always happen thought but it happens more then not, and one of my exhaust blows smoke out and you could see but not so much the other side does anyone know the problem please help?  

sounds like a transmission problem. your gears might be worn down and the whole assembly may need to be changed. depends on the car, some are better than others.