We are in Vermont with a 1998 Pathfinder that has 115,000 miles and two problems. My question for you is do you think they are related, and if not, how to fix?

The service engine soon light came on and mechanic says it was fault code 1491. The code refers to the "vacuum cut bypass valve" and he did not know what that was, so he reset the warning system to turn off the light. I was hoping for something more thorough and after looking on internet I found a service bullitin DTC 1491 that explained where the part was and how to replace it. We decided if the light came on again then we would order the part and follow the service bullitin replacement directions.

The other problem I am having is a loss of power when going uphill [a big problem in Vermont]. The fuel filter is fairly recent and my mechanic does not believe it is the fuel pump. He thinks the exhaust system could be partially blocked mainly because the sound is different while attempting hills.

Could a faulty vacum cut bypass valve be responsible for no power uphill?

Is there anything else besides a partially blocked exhaust system that could be responsible for the hill problem?