Could be anything mate, really. If its hesitating when revving, might be the MAF or O2 sensor, then again, hesitancy in the revs could be ignition retardation caused by knocking, but I'd imagine that this would only happen at really high revs. May also be a coilpack, possibly plugs!
I'm really not the best person to be advising you TBH, but if you could at least eliminate the sensors by placing known good ones in - perhaps borrow them from a fellow Scooby driver. The MAF is the easiest to change but the O2 one is a big more difficult given its location. If you don't have to wait long for the diagnostics, probably be better just holding off.
Hope it goes well, mind post up what was wrong.