What can cause the passenger side of my motor to be warmer than my drivers side?

Background: I started noticing a slight burning smell and couldnt track it down. Brakes are wearing normally and dont stick so its not a stuck caliper. Shop replaced the a/c resistor and cleaned some leaves out where they had fallen down through the outside vents. This helped but then I still noticed the smell. I replaced the belt and radiator hoses and replaced the coolant that came out (partial coolant change). I then thought the engine could've had crud on there so I sprayed it with engine degreaser and hosed it off. Still smell it. This is when I decide that the passenger side definitely is warmer than the other side and the heat and smell appear to be coming from above/ behind on the passenger side towards the firewall.

What can cause this? Plugged cat would cause it to run funny and it runs normal. No mpg changes either. O2 sensor problem? No codes showing. Im going to get an infrared thermometer so I can tell what exactly is getting warm.

My truck: 04 dakota 3.7L quadcab, fastman TB, Taurus efan with dccontroller, air intake, flowmaster 50 series muffler

Thoughts? Ideas? I just want to figure it out.

 

coolant ports clogged on that side of the head not allowing to cool properly? i dunno.

 

Then perhaps I need to flush it with the proper detergents and a hose. What else?
BTW there's about 123k miles

 

You you still have tge cats installed. The passenger side is probably bad and overheating.

 

See if you can find someone with a temp gun and find out how much hotter it is than the other side. If you cant find a temp gun go to lowes and buy one then return it when your done lol.

 

I never updated. It ended up just being hot @$$ steam coming from a very very slight oil leak that was dripping down onto my exhaust pipe. The steam/smell/heat was what I was feeling. Replaced Head gasket and the leak was gone and smell/occasional smoke/steam was gone.

 

If you have the stock fan it spins most of the hot air to the right side of the truck.. the fan is off set and more hot air is pushed to that side.. where as if you put an electric fan on and it's center of the Rad.. you'll have slightly equal temp on both side.

Also there is slightly less room on the right side; airbox; and motor sits farther to the passenger side.. and so on..

Just throwing it out there.