Surging at part throttle

[Kaeden]

So i recently did my ignition system on my 1988 ranger with the 2.9. I did everything the plug,plug wires,coil, whole new distributor everything. I set the initial timing to 12°btdc and now it surges with the throttle cracked open. It idles a little low and rough. it stops surging once i give it some more throttle. I checked the timing with a light after everything and it was around 15° to 17°. Is my timing too advanced or is it something else.