-IPA has a RON of approx 118, so yes it will work as an octane booster.
-It is very good as a cleaning solvent, although I'm not sure about how well it will remove deposits from inside an engine, as I'm unsure of what they are primarily composed of. It is also a solvent for rubber, so I'm not sure I'd be that keen on using it in a cars fuel system.
-It is an oxygenated fuel, therefore it will make your car run leaner.
-It is miscible with WATER, which is what I see as the biggest disadvantage, if left in an open container it will absorb moisture from the air, and it will allow your fuel to hold more water which isn't always the best.
-If using it be careful with it, as it is toxic by inhalation and absorption.
Of course all this data is based on IPA by itself, goodness knows how it will react in low levels in a fuel mixture.
It is your car and you can rely on the advice of who you choose, although in this case I would advise against it's use.
Let us know how you get on if you decide to go with it.
chops