22r issues

[PorterFNU]

I just bought an '86 Toyota 4wd pickup with a 22r/2 bbl carb motor. The truck has 219k+ miles on it. Previous owner replaced motor with one that has around 90,000 miles on it. It had a muffler that was blown out at the seam and no tailpipe coming from rear of muffler. While I was driving it home I realized it had a nasty backfire/muffler expolsion issue that occurred mainly on deceleration. I replaced the muffler/tailpipe hoping that would solve the problem. It didn't. I've since noticed an exhaust leak/smoke coming from the downpipe area. I live in NJ so I had to get it inspected for emmissions. It failed miserably. CO2 is supposed to be in 220 ppm range, it is currently above 800. I've changed the plugs, wires, rotor and distributor cap. I have also reset the timing. It starts right up, idle is a little rough and runs fine (although not very powerful, this may just be because I'm comparing it my other vehicle).
In short, here are my symptoms:
formerly blown out muffler (now replaced with OE matching muffler/pipe,
exhaust leak/smoke coming from downpipe area,
nasty bakfire/muffler explosion (mainly on deceleration) usually accompanied by what sounds like a wire brush being rubbed on metal and a metal on metal clanking noise,
Extremely high Carbon Dioxide and Nitrous Oxide (not sure if nitrous is correct, it failed for NOx and I'm assuming that is Nitrous). Both are in 800 ppm range.
Any help or suggestions will be greatly appreciated.
Thanks.

[fourwd1]

To start with it sounds like you are running rich (too much gas).
Could also be a timing problem.
Also, in a 22R that old the EGR passages could be clogged, from the valve all the way into the intake manifold. I've had mine completely blocked solid with carbon.

[PorterFNU]

Originally Posted by fourwd1

To start with it sounds like you are running rich (too much gas).
Could also be a timing problem.
Also, in a 22R that old the EGR passages could be clogged, from the valve all the way into the intake manifold. I've had mine completely blocked solid with carbon.

Since my original post I've discovered that at least part of the problem is a damaged Auxiliary Accelerator Pump diaphragm. I disconnected the vacuum hose and plugged it. Aside from it being hard to start the backfire is gone. It's only a temporary fix. I'll have to change the diaphragm to make sure that's the problem.

[fourwd1]

That would make it run rich.