I removed the pre-cats and the main cat, also installed the Walker Dynomax Polished Turbos. Sounds real good from the outside, and the engine and actual exhaust is great from the inside. Its the resonance that kills me! I tried blocking one of the exits on each muffler with a rag, and it works great, but I cannot devise a good method of capping them, especially since they are rectangular. I am also pretty sure there is some performance loss, wich i could live with as long as I could remove them easily. I went by the muffler shop, and the guy said its because of not having a cat on it. He said put on a high performance cat and it will go away. What do you guys think? I hate the thought of it! He said a 3 inch Ford truck Cat is as high flowing as they come. Will give it to me installed for $175. I wonder what it will do to the sound, SOTP, and ET? Any thoughts?

Also, pulled the plugs the other day. Came out real clean and dry, the center electrode was a dark grayish brown, but the rest of the plug was jet black, almost like ash. Is it too rich? The AFPR is at 52 lbs, will lowering it alter the mixture? Or could it be that without the cat the O2 sensor doesnt get hot enough and let the computer do its job. The car is running great, I would like to get 13.3 out of it before doing major mods. What should I do about the plugs, AFPR, and next mods (cheap!). Check sig for mods.

Thanks guys!

 

a cat might modify the resonance, but it won't go away. might not even make any difference. it just depends.

in my experience, catless cars tend to resonate less. although, these cars usually have different cams, which also tends to lessen resonance, so it's difficult to make a generalized statement like that.

well, it's not difficult to make the statement, just to back it up!