ok, so if i let the truck sit and idle... the idle will start to drop until almost and sometimes stalling... when it does this, it sounds like it develops a big vacuum leak... if im driving it, its fine but even if im waiting for a red light it will start to die out... when i let off the gas to coast to a stop, the idle gets real low for a second... im stumped, please help!!

 

Replace the pre-cat oxygen sensor. Guarantoldja.

 

+1. You can also just unplug it to see if it will make a difference.

 

You might also consider removing the IAC and cleaning it. Look in the FAQ, I think there is a DIY.

 

when i bought the truck, the kid told me he hollowed out the converter... would that have anything to do with it?

 

No, and that is actually a good start. Do a search here for "plenum". And replace the pre cat o2 as suggested, as it can be bad, but not throw a code. Problem is, even if it is bad, it is not the root of the problem. Do the plenum search as I suggested and you will learn a lot. And since you have a 96, you might also have an EGR problem. But not as likely as the plenum.

 

My truck is actually a 1997 with the 360 engine... made some calls and turns out my truck has a left and a right upstream sensor and they are different prices... do i need to replace both? or is one more likley than the other?

 

You made some calls? How about getting under it and looking? If it has two PRECAT o2 sensors then yes, replace both. That means it has California Emissions setup. (Odds are it's not depending on where it originated from, and has only a pre and post cat sensor) Federal Emissions setup. Get off the computer and look! LOL

Btw, all you have to do is open the hood and look at the VECI sticker to find out what emissions it came with.

 

lol, i just woke up! im headin out to buy the sensors now... the calls were to autozone and murrays for prices, they told me i have 2 precats lol

 

LOL, LOOK and make sure before you spend money for no reason.