2001 exhaust help!?

Need exhaust help...
I have a 2001 double cab 4x4. The rust has created holes in the muffler, in front of the second catalyic converter on the top of the pipe. Looks difficult to patch. The second o2 sensor, after the second cat, isn't even bolted on tight. The bolts on the sensor are rusted tight. But I have no check engine light.

I have researched into the magnaflow 2.5 cat back exhaust kit. I'll moat likey buy this when my taxs get here. The direct fit magnaflow cats are like $300, compared to a universal magnaflow cat which are 100$ If I were to get the universal, and weld it together, to try and save money, would that make the check engine light come on? Are there any down sides to this?

 

BUMP ^^^ Same question.

 

As long as the sensors detect a difference between the front and rear and it changes the MIL should not trip.

A leaking exhaust will also cause the MIL to trip.

I hear stories that it will trip once the cat efficiency drops below 98% 97 % who can say.

So far my Walker cats are working.