Knocking noise? Unsure what it is...

Could it be exhaust leaks? I found a pretty bad exhaust leak near the main cat and the heat shield over the cat us loose as well...

Paycheck to paycheck minitrucker

It could be the heat shield for sure. Those things are notorious for rattling. They generally have a real tin sounding type of rattle if that makes any sense at all. I generally either tack weld them to the convertor body or cut them off all together depending on how close it is to the floor pan.

I'm leaning towards this because the noise is loudest near the middle of the cab...

Paycheck to paycheck minitrucker

A convertor rattle will typically change pitch and some times start and stop at different times through out the rpm range. Just different harmonic effects on it I guess. Most generally the ones I've seen have been the loudest at idle though.

I had trouble with my heat shield on my downpipe before the cat rattling at idle I just removed it though... It was kinda like the sound I'm dealing with now...

On a totally different note I changed the oil today and after I changed the oil the truck smoked bad for like 5 min then cleared up is this a normal kind of deal?

Paycheck to paycheck minitrucker