All of a sudden, my battery light has come on and the engine has gone crazy - it all of a sudden revs up, then goes back to normal...does it again, etc.
Any thoughts? Thanks!

your alternator could be going out as well as the intake manifold gasket (IMG)could be going bad...at the same time.

do any other lights such as abs/trans/ oil come on? this would indicate a bad alt.

as far as the revving issues, indicative of a bad IMG ussually.

Yeah, go get the alt tested. This is exactly what mine did just before the alt. finally gave out last month.