all right I bought a cam about a year ago and waz going to get a header to, but I had to buy tires b/c dour boxes of nails fell off a truck that I behind and I ran over the boxes. So now it is time to do the timing belt and I have the money to get all the parts to do the cam or should I buy a header first?

 

not sure what other modifications you have done but if you have a sxt/se which has a 2'' exhaust piping the maximum HP you can flow through that size exhuast is about 130hp (or stock) and the stock muffler does help any. If you have the R/t ACR 2.25'' exhaust than you are good for a little while.

So I would focus on exhaust mods before a cam change but if you are going to change the timing belt DEFINITELY put the cam in while you are 90% the way there. also any exhaust mods will be amplified by the new cam.