Mitsubishi Repair: Air Filter System - Temp Sensor ?, air filter system, emissions test

Question
There is a large air sensor unit in the air filter hose, just after the air filter box. The young man I bought the truck from has put in a KN filter and removed the guts
from this sensor unit.  It will not pass emissions at 25mph.
What is this unit and where can I get a replacement. Its unplugged now and runs ok - when I plug in the unit - the truck will not even run, backfires, chokes out, runs rough.. When I unplug the unit again - it fires right up but the guy said its not burning all the gas and I get a high co2 reading on emissions test. Can it be bypassed some how or is there an aftermarket unit ?  Thanks

Answer
Gary: You might try a junk yard or else you will have to buy a repair manual for your truck can get one of those at most parts stores for around $20.00. It would explain just what all you need. Or else got an AutoZone close by, I have heard they are good about helping people like yourself. You could explain the problem to them and ask about any aftermarket unit. As I don't do a lot of such work and so don't know about those things. But I don't think it can be bypassed because of the computer. It has to have everything set up as the law wants it to be. I guess I would try a junk yard as you might be able to buy the whole unit for less money then new. But still if you want the truck to pass the test and run you will have to do this. I would say this young man did more than just unplug something and pull the guts out. He had to have played with other things. But you won't know till you get that whole unit. Of course once you put that unit in, you will have to get the computer to remember it too. But when you put in the unit, unhook the neg cable from the battery, wait 5 minutes and hook it back up. That should clear the computer and then it should find the new or used part that you put in. I wish I could help you more. But check those junk yards and check what the unit will cost new; hope you are sitting down. And check on a aftermarket unit but I bet if there is one that would be costly too. I know my son had somewhat the same problem only with a car he bought. And he ended up going to a junk yard, getting a whole unit and replacing all that the other person who owned the car before had done. So that he could pass his emission test. Hope this helps some and good luck! Linda