Darrel wrote the following at 04-11-2008 7:59 AM:
"998
engine. Accelerates smoothly to 50/60 miles an hour and cruises there
with no issues - as long as the road is flat. As soon as you hit a
hill and place more load on the engine it starts to "misfire". ...."
Were the valve guides replaced recently? This sounds like a valve sticking open when the guide gets hot and expands (inward) under higher load and heat conditions. Bronze guides are particularly susceptible to this as they expand more than iron, so they need a tad more running clearance.