LongTube question
 

Will I need the MIL eliminators if I were to install long tubes and I were to keep the cats?

Its a crap shoot because of how far the cats will move and how long it takes to heat the 02 sensors you might still get a check engine light with them and long tube headers.

I was doing some reading, and from what I gathered I would have to delete two of my cats and then maybe get some other highflow cats. Or could I simply just move my stock cats back and intergrate them into the headers etc.?

If your getting long tubes I would hope you get rid of the stock poor performing cats and add in two highflow cats in there place. But like I said when you move the cats down along with the 02 sensors down and farther away from the engine where they heat up faster they can cause some weird 02 sensor readings. Don't you have a tuner on your car? If not screw the MIL's and save that money towards a tuner.

get a tune. moving the sensors further from the cylinders induces a delay that affects the tune. you need to have the O2 sensor delay value increased, which will require a custom tune.

As for cats, don't leave stock cats on it. Use high flowing aftermarket units. They're good and efficient but they flow way better.