try cleaning the little jet holes under the rim out with a coat hanger wire. It makes more difference than you'd think, plus it doesn't cost anything (well maybe a coat hanger). Also make sure the hole at the bottom front is not clogged up. Between the jet holes and the hole at the bottom, that is where all the water from the tank comes out of. If either of these is clogged (or partially clogged), the water will flow slower and reduce the amount of force it comes out with.