How much total horsepower will i have?

I have my custom exhaust system, pictures to be up soon. It is very similar to the dynomouth, so you can figure about the same flow. Im planning on getting a lid. I would like to know what the lid will ACTUALLY get me, not some advertisement numbers. I would like an idea of the ball park figure of my total horsepower when both mods are in place.

I was also wondering what is a brand of tires that are pretty cheap and have some hella grip in case i race once in a while?

Thanks guys!

Figure on up to 7 rwhp for the lid. The dynomouth should net you around 10-12 rwhp so I would figure on having in the neighborhood of 300-320 rwhp depending on the tranny you are running and how strong your car was to start.

As far as good cheap tires, I love my Bridgtestones. Not to great for straight line work (really stiff side wall) but awesome in the twisties. My car on 16's handles about as well as an SS on 17's (mind you the SS has the upgraded suspension). 126 a pop from tire rack for 245 50 ZR16's. I have 7000 miles on mine or so with 75% tread left, and thats going through about 7 autocrosses with them.