I have a Toro Z-Master 74240 that is electronic fuel injected w/ a 27hp Kohler. It seems to bog down and not run right. At first, I thought maybe it was just a problem with the seat sensor (b/c it began intermittently) but have now ruled that out. I have replaced the o2 sensor and an ignition coil but neither resulted in any improvement. It is not firing correctly on one side. Any ideas or suggestions? Thanks in advance!