If there was a major vacuum leak you would get thrown P017X codes already.
You already addressed the P0543 EVAP issue so what other codes do you have now.

 

If you haven't checked the EGR valve yet, just make sure it is fully closed and not being held partially open due to carbon accumulation..


It sounds like the converter is restricted.
Do you have a vacuum gauge to use ?

 

im thinking about the converter, i will have to buy or rent a gauge. do you know the specs it should show? like normal pressure vs pressure that indicates a clog?

 

i havent addressed the EVAP code yet i didnt think it would cause this issue

 

You might have provided the wrong DTC above.
P0543 is relevant to intake air heater, nothing to do with EVAP.
EVAP problem, in addition to fuel vapors, can definitely affect your Air/Fuel mixture causing the symptom you are experiencing.

 

i meant to type 453 thats my bad. it says evap emissions circuit voltage too high

 

everything ive read online says its either the FTP or the harness it plugs into more likely than the sensor itself idk

 

what i read online kinda said it wouldn't cause the running issue ive had idk lol im not sure but that's the actual and only code present

 

If you connect the vacuum gauge to a source of manifold vacuum , engine idling should be in the area of 17 in vacuum to 19-20 in.

The way you test for a restricted converter is: when you raise the engine RPM and hold it there, the vacuum reading will keep falling because the engine is having a hard time breathing. If you get that result, you can be sure the converter is restricted .
Your diagnosis doesn't stop there, however, because repeated constant misfires will overheat and melt the substrate inside the converter creating resistance to good flow through the converter.
If your engine was running rich for a pretty long time, that means the converter was working overtime trying to clean up the exhaust and getting overheated during the process. Lets see what the vacuum gauge reading shows , OK ?

 

bingo sir. thats my guess mr hanky. my gramps mentioned the engine had water in the two plug wells cuasing the injectors to dumb raw fuel on the inner two cylinders. he said the cat was glowing hot. he got the water out and it ran ok but slowly degraded afterward until we got to where we are. im thinking that cat is clogged/melted. i will have to perform the tests you mentioned above. so it should be about 20 psi, or inches over mercury or something? and if it drops off thats our indicator?