I have a Briggs 5HP 130202-0801-01 engine on my log splitter, and it runs decently but since last season it started to bog down here and there when put under a hard/sudden load of a big log. Seems as if the low speed adjustment is off. I'm not sure what adjustments to make, or if there is another issue. There is one screw or plug that seems to be missing, but I don't think it's an adjustment screw. I'm attaching a picture for reference (the air filter is removed here) The threaded hold just below the air intake is the screw that appears to be missing.