1992 EXT 22re 4x4 5 spd man 254,000 miles

So I'm driving down the road and turn on the heater and all of the sudden the truck starts making a loud noise. To my ignorant ears, the engine sounds like a diesel now. By that I mean loud and kind of exhausty and poppy. My buddy who was with me says its a ping noise. Doesn't make the noise idling, only under load. Noise seems to be coming from the rear of the engine. I wouldn't be surprised if the timing guides are broken, but I don't think that is what is making this new noise.

No CEL, but codes read 13 and 42. (The speedo stopped working a few weeks ago, not sure if this is related)

I'm finding conflicting information online and am hoping for some good places to start. All the connections (I am aware of) seem good. How would I know if the ECM is bad (other than buying a new one)? Or for that matter the EGR Valve, Knock Sensor, Air Flow Meter, TPS, or the many things other things possible?

Any advice is much appreciated. Thanks.

 

13-rpm signal to ecu missing above 1000rpm
42-vehicle speed sensor
Wish I could help you more but I'm a noob at 4runners

 

Yeah, I got those trouble codes. I just don't know where to start, what to do.

 

Anyone?