i have heard that a lot of methanol in the gasoline might fix it. it will run poorly, but it might pass. i dont know i have not done it my self. try 50 to 70% of what is in the tank. a different thing is find a way to pump lots of just air in to the ext pipe as close to the engine as you can

 

Have you pulled off the O2's to see what they look like that will tell if they are old burned units and give you an idea of things O2's are not that pricy for the Dakotas.

A tune-up is a good thing air filter so on.

The cat if its bolted on remove the bolts and look inside it.

If the cat looks very old its likly in bad shape.

If its a bolt on cat replace it yourself and save the $$$

I had my exhaust completely redone new cat, muffler and pipes and the shop welded everything kind of pissed me off I guess its stronger welded but problematic for later replacement.

 

Thank you all........its time for me to move on to something more substantial now. I am going to spend the next little while reading up on the forum about how to get more POWER out of my 318. Plan is to touch 300 whp and 400 torque without any change to internals. Think it can be done?

My experience has motly been with Skyline GTRs, so American muscle is kinda new to me. Not sure if you can put snails on this engine (likely not, since it is over 200,000 miles old), but it would super cool if you could and also use the stock PCM to control everything on it.

BTW, does anyone know the stock injector size on the 1999 318 V8 Magnum?

I truly and deeply appreciate the inputs you all have given here. Cheers....

 

I wonder if anyone has removed a cat smacked it on the ground or a hammer to pop some crap loose works at all for a temp fix on a cat my understanding is they get pluged up so I wonder if smacking it around could give a temp fix?

Probably best to replace it.

 

i think the only way you can get 400 ft lb tq is to run nitrous with stock internals but i wouldn't recommend that. if you do exhaust, tune, aka basic bolt-ons you still wont be close get close to that. you need a cam at the minimum.