I have a 460 EFI in my buggy and it idles rough when the engine is cold. I did a compression test: highest was 171 psi and lowest was 132 psi (within 75%) all other cylinders were 150 psi and higher. Injectors and fuel pressure is good, 39 psi with ignition on and 30 psi at idle.

The motor seems to be missing as I revv it up, and when I give it gas really fast, it will sometimes backfire through the air filter.

I pointed a timing light at the timing marks and at idle the timing is 20° steady, not sure if it's good or not.

I have a feeling it's an ignition timing problem, but I can't adjust the timing on these motors, right? is there a crankshaft position sensor? I can't locate one.

I changed the plugs, dist cap and rotor, and the resistance of the coil is 1 ohm at the low voltage terminals (specs are 0.3 to 1.0).

Not to mention that the motor lacks power.

Oxygen sensor tested good also.

Anyone have an idea? Thanks.

vacuum leak? had similar issue with mine and thats all it was.

No leak that I can detect, although, I did connect the opening under the oil cap straight to the opening under the throttle body (both 5/8" ID hose barbs), I'm not sure if this is correct.

Plug that hose comming ouyour intake that you have hooked up to your oil cap and see if the problem goes away. That port under the oil cap usally goes to the air box, not the intake.

An 89 should have a "spout connector" . You need to unplug it, this will keep the computer from adjusting timing. Then you can set your base Idle, I prefer 10 btdc.
You should also try blocking off all vacum lines till you have it figured out. I have seen brake boosters, distributor advances and cruise controls cause leaks..hope this helps.

Thanks guys, I took off the spout connector and set timing at 10° BTDC, connected it back up and the engine is running great now!

Where does the opening next to the oil fill plug get connected to?

That should connect to the air inlet, probably just after air filter....that brings fresh air in, and your pcv pulls old out, pcv should go to the manifold.