We just bought a 2008 Sentra SE R 6 speed manual trans. I love the car already but it does have some issues. The car has a 2.5 engine and I am concerned that this engine might go the route of the 2.5 pre-cat Altima problems. I haven't had a chance to run a scan on it yet so I am still in the dark about what codes it will spit out. Any information on a pre-cat problem on this car? Should I swap out the Catalytic Converter?

I read somewhere that the straight stick 2.5 Sentra engine didn't have a power valve like the 2.5 Altima. Therefore no worries about the screws coming loose in the power valve and dropping into the engine. Is there any truth to that?

Now for a problem that is really bothering me, when the engine is cold the engine doesn't stumble at all, only when it gets to full operating temps. It usually stumbles or bogs down at about 3000 rpm and accelerating in third gear. Would a bad catalytic converter maybe cause this?