It's near time for me to have my exhaust line done, 2.5, cherry-bomb muffler and i'll have a magnaflow 14106 off-road cat put on it. Will it have provisions for an o2 sensor or does it just not work anymore with it being straightthrough?

 

I'm assuming that you have a '96 or later. Also, what's an "offroad cat" typically there's "offroad Y pipe" which has no cats, or there is a catted Y which is street legal. Nonetheless, if you have an offroad Y you should get O2 sims so that your computer doesn't throw a code.

 

It's essentially a cat that's empty. Not like a gutted cat, because it has a straight-through pipe in it with a perforated core. No emissions control BS.
And no, i have an '88. Does this change something?

This is what i mean
http://www.car-sound.com/02product/universal/race.asp

 

Ok, so it's pretty much a hollow piece of pipe that looks like a cat...either way, since your car is an '88 you won't have to worry about it because you don't have O2 sensors after the cats, all you have are the 2 in the manifolds, which the cat doesn't effect, so you're good to go(providing you don't have to pass anything other than a visual emissions test).