i have heard that installing aftermarket pulleys will increase hp. Which pulleys need to be replaced? And how much will they affect performance?

 

You will need to replace the under drive pulleys. Some say around 15 hp.

 

Is it difficult to change out the pulleys? Will i have enough room to change them without pulling the engine?

 

I think you will. I am not positive because I haven't done it, but I think it is possible. Look under you car and it is the pulley farthest to the bottom. I know in my firebird that I can fit a big wrench under it, it will be really tight on the though and you will need a breakerbar which will fit.