I say it might add a few HP, but nothing huge. O2 helps things burn hotter. When the O2 is decompressed from the tank, it's waaay cold. So when i enters the engine, your engine is much cooler. But i think it won't be as effecient because most of the o2 will be unused, and of course, be let out as exhaust. this is just my theory, and my .02. I may be wrong, but as i said, it's just my theory.
