My 914 had not run for 3 years. I soaked the cylinders in WD40 for a couple days before starting. I discovered heavy rust in the fuel tank so I replaced:
Tank, hoses and pump.
Injectors and engine bay fuel lines
And Flushed the long fuel lines until they ran clean

The engine started but there was no power, poor idle
I Replaced:
Points/plugs/condenser/coil.
Reset timing and idle (The dwell is no high side- 58)

Power is back and idle is good.

The Problem:
When I give it gas, it will back fire into the throttle body. It seems to happen a 2k - 3k rpm range. It's doesn't happen every time.

Ideas?

Have you checked valve adjustment?

A couple of questions / points:

1. Which engine (e.g., 2.0) / injection system is this (or is it not FI)?
2. Were you seeing symptoms of something when you stopped driving it?
3. Agree, valves worth checking
4. Set dwell to 45 - 50 and THEN set timing. Changing timing will alter dwell.

Oops.....it's 2l with FI. I will reset the dwell and timing...and then the adjust the vales. thanks for the suggestions.

The motor ran ok before its nap.

Double check your firing order on the distributor cap. Two swapped plug wires can cause a backfire and sluggish running like you describe.

Yeah, Clay's got a good point. Esp. since you had the cap off and were doing some ignition related work.

Here's a visual reference:
Click to view attachment

Thanks for the responses!!!

Last night I reset the points gap and got the dwell within specs, and then I reset the timing.

The problem is now fixed.

Excellent!

What part of VA are you from?

Glad to hear. You don't need your throttle body damaged do to a serious backfire.