Yea, I've pretty much tried all of the stuff that you all mentioned. Let me just say...this tar is no joke! I'm thinking of using "Airplane Remover" to get it off now. Yea, it'll eat the paint, but I don't mind. I have to keep my interior to stay in my class, so it'll just cover it up.
And yes...I'm removing it b/c of weight. I've heard numbers ranging from 20-40 lbs. of weight shaved from this stuff, although I think that 40 is just an "over-exaggerated ricer number". If I can get just 20 I'll be more than happy.