For the most part you'll have to be on a dyno to tell the differance. Typical incease is 10-15 HP on some engines, depending on the overall combo you might only see 5 hp. Even if it is 15 hp you wont actually see that in the water with a jet or hydro when you figure out on the upper end how much more power it takes to turn another 100-200 rpm's. It takes alot more that 15 hp.
The 4 hole might help it idle a little better and a tad better on transition. The 1/2" 4 hole on top of the 1" open isn't a bad idea. You might want to try a 2" open.
Sleeper CP
Big Inch Ford Lover