2007 SLT 1554 only 450 hours. Have had issues for a few years seems to lose power cutting grass on an uphill grade, I have replaced the spark plugs, fuel and air filters, fuel pump, carburetor nothing seems to help really. Not much more it could be any suggestions. Tractor is in pristine condition and maintained the same way. It doesn't die just you can feel the loss of power on grades significantly.