I'm adding trick flow aluminum heads, headman headers, and porting/polishing the intake,plenum, and new SLP runners. will I need a new chip just for that stuff? and if so how much will I benifit from one? thanks!

 

You only need a new eprom if you wish to have your engine perform optimally. How much will you gain? Depends how "off" your current eprom is.

Instead of thinking "how much HP you will gain", you should think "how much HP you are throwing away" with a "less than optimal" eprom.

Read Tim's (Traxion) eprom burning intro to see what equipment/software you need. Once you have all the equipment then you are dealing strictly with "tuning" issues. The more effort you put into it, the better the results you will get. Buying an eprom from someone else MAY get you close, but generally will not get you an optimal eprom unless they are doing actual "hands on" testing (which none do).