Suggestions for removing smoke stains from a marquee?

[2PacMan]

I bought a Vs. Super Mario Bros and the marquee is badly stained a yellowish brownish tinge due to what i'm assuming to be smoke from years sitting in a bar.  Under the marquee brackets, the thing looks brand new.....anything i can do to remove this discoloration?  I tried soaking it in Oxyclean and several over the counter general spray cleaners, but nothing worked.  I'm worried if I use too harsh of a cleaner, it will eat away the print on the marquee.  The Vs. marquees are like vinyl stickers stuck to the outside of the plexi, so there is nothing covering the printing.

[Luckydevil]

Maybe try some rubbing alcohol on a small part that doesn't show just to be sure it won't mess up the marquee. Then try cleaning it with alcohol on cotton balls.

[Witchboard]

I got one monitor that was so badly coated with nicotine and tar that I had to use paint thinner to cut it.  Obviously you can't use that on a plastic marquee, but maybe you can try Lift Off #1 or #2 or something.  They have a little kit at Home Depot with #1-3 and each one is more powerful than the last and it says it's safe for vinyl, lexan and plastic.