1991 Acura Integra my car's pickup or power was not right

1991 Acura Integra mileage: 158,000. After doing, a lot of research I had a rebuilt engine put in my car a year ago. My car has been running like a dream. I do approximately 300 highway miles a week. About a week ago, I notice my car's pickup or power was not right. It feels like I am towing something or my a/c is on. Can you give me any answers to this? My mechanic told me it might be my air filter, my fuel injection filter or a pinch hose.