I bought a neww Z225 42" cut a couple years ago. Bought a mulch kit at the same time. The cut is terrible. I have tried new blades, aftermarket (Oregon?) blades, but nothing seems to help. Motor, belt, and tensioner are all good before anyone asks.....it seems the right blade always leaves a streak. It's like I have a 21" cutting mower. The mulcher paperwork says something about there being a left and right blade, but every time I order the blades are identical(either OEM or aftermarket). Any suggestions.....I am about ready to trade it in on a different brand. HELP!!!!!!!!