2000 Ford Ranger

Before winter I had noticed that my Ranger was acting like the engine kept shutting off. After several times of barely making it home and one time of having it towed to my local garage, I decided to have my mechanic check over the entire engine and fuel system. He replaced the fuel filter and said that a vacuum line had been unhooked somehow. I decided to only drive the truck in severely bad snow storms (because of the 4wheel drive) and now that it is spring I started driving it reguarly. Now, it seems that the truck is getting sluggish and taking longer in gear to gain speed. When I go uphill, the truck barely wants to keep momentum and loses power quick, then when I shift down to 3rd, it feels like the engine stutters from time to time as if it has a miss. Thus, I checked and replaced all spark plugs and wires, but it still didn't help. I tune up my truck way before it's due and change my oil religiously. I don't really know where to start to try to fix it's sluggishness. If someone could get me pointed in the right direction then I might be able to solve the problem without emptying out a bank account or two. Thanks.