84 LeSabre loss of power, high idle, stalling in reverse
 

Hey guys, had a few questions. Recently picked up an 84 lesabre, it's got 80k kilometres on it and the engine seems mechanically sound, its a 307 olds. I've been driving it short distances, doesn't stall unless I'm in reverse and don't give it enough gas.

When I get up to highway speeds it stutters and I experience loss of power. I've been doing a bit of research on it and discovered it could be a vacuum leak somewhere, I don't hear anything but I have a pressure tester so I can test it, problem is I don't know which line to go off of. There isn't a whole lot of info on pressure testing this particular engine, that I could find anyways.

Also might be the fuel filter, I ordered one and am due to replace it, something concerned me a bit though, whoever owned this before me, JB welded the large nut. Don't know if there was a leak or something, not sure. Will I still be able to take the fuel filter off or am I ****ered? I have to use 2 wrenches to take it out, is the JB weld just there because someone didn't want to mess around with 2 wrenches? Maybe stripped it? A little concerned about that one.

I'm a little bit new to the scene, I haven't owned a car with a carburetor before so this is all new territory for me, I know it's not the ideal carbureted engine to start on. The carb looks gummed up, so it could also be that right? The damper doors seem to be functioning but I'm not sure if the carbon build up would have an effect on what's happening to the car. If I had to guess its got something to do with the fuel, either the injectors or something else.

I thought one of the lines might be frozen since the guy told me it's been sitting since July and it's now winter, I live in extreme cold. I put de icer in there and some sea foam, to clear out the lines and injectors hopefully but it did not work unfortunately.

Does anyone have any ideas for what it is? Any knowledge or tips would be appreciated, trying to learn as much as I can about these old engines. Thankyou.