I purchased a 1999 Toro Z325 from a local dealer. He owned it since new and had sent it out as a demonstrator. It kept coming back with no buyers. It had 150hrs. The dealer was not a hard sell and indicated that it was not easy to control and clogged quite often. I was set on an internal bagger and bought it. I replaced the control lever dampers with a retrofit kit. It controls very well now. The engine, Kohler 25hp, got a head bolt retrofit to prevent head gasket problems. I used it all summer and it did clog under many different conditions. The mower was always caked with wet grass and in some stage of being clogged. I was about to get rid of the machine. In the sequence of trying things, I noticed that the idler wheel spring on the blower was quite weak and the belt did not have much tension. To make sure the belt was not slipping, I sprayed it with belt dressing. The machine has never clogged since then. The mower never has any grass stuck under it. I am now through the leaf season and this thing picks up everything at any speed. Leaves are even pulled in from the sides of the mower. IT now works better than I hoped for. The belt never made any noise, and I don't know how you would know it was slipping, but it is the key to this unit's operation.