I own an '89 Safari with the TD42 non-turbo. It's been running poorly. It's acting like it's fuel starved (sputtering) above 1500 rpm. The air filter change didn't help. I have a new fuel filter< but the old one won't come off. Any tips? It looks old. I've owned the vehicle since '09 and had it regularly serviced, but I don't recall the fuel filter being replaced. Threads on this site, plus a helpful member (thanks Chimo!) have also suggested air is getting into the system via the fuel lines, but they look sound on this one. Plus, I'd like to see how a new fuel filter helps before delving deeper.