All the fooler does is prevent the computer from going into limp from overboost. THAT'S ALL IT DOES.
To get more power, you need to turn up the wastegate as well, and to get any real power, you'll need more fuel.
Having said that, you completely could pour out another 100 hp by running the boost up to 30 psi and adding another 100 hp of fuel. Adding the fuel without the fooler and wastegate mods would probably only net 50 hp or so, and the egt's would be way out of hand. With the hx turbo, you probably could see 125 by adding adequate fuel, and going to 35 psi.
I strongly advise against completely disabling the wastegate. It won't rob power by opening if adjusted properly, it will simply allow excess flow through. This prevents choking the turbine and excessive pressures that garner little performance improvement, but MASSIVE jumps in engine destroying pressure and heat (egt's). One other feature of the wastegate is to drop the exhaust pressure on the exducer fan limiting the maximum rpm of the shaft/impeller. This prevents overspeed of the turbine assembly, which can scatter the impeller.
Disabling the wastegate, or adjusting more boost from it will make the computer go into limp, and won't make more power. The fooler prevents this, and allows more boost, and thus more potential power. Many chips have this feature designed in, making the fooler superfluous if you plan on getting a chip. Then all you have to do is get a boost elbow (hy35) or cut the wg hose and rotate the housing to turn up the boost (hx35) I have heard it is possible to adjust the hy by turning the rod, but I cannot verify this, and the boost elbow is sooper easy, and takes you hy right to the limit (30psi)