Backfire through throttle body

My 1984 2m4 will start and run but when more fuel is added it seems to backfire out of the throttle body . I have a feeling it is a valve related problem but not sure . There has been a ticking sound from the valves for a while . Any ideas ? It has really low km's ... 110,000 or so ... I am going to check the oil pressure to make sure the bottom is working fine before i go too deep from the top .

How is the timing?

The Hayne's manual:
1. Emissions system problem
2. Timing incorrect
3. cracked spark plug insulator, plug wires, distributor cap or rotor
4.Fuel injection sysyem in need of adjustment or worn excessively
5. Vacuum leak at injectors, intake manifold or vacuum hoses
6. Valves sticking

I did change the wires and plugs , but i now wonder if the distributor cap is in the right place or if it is off just a little . I will check the timing for sure . Great tip , thanks .

Yea, timing would probably be the #1 thing to look at. In my past experience, 2.5L 4 cyls seem to pick up leaky valves rather easily, but CHECK THE SIMPLE STUFF before pulling the head off. Your clicking noise sounds like a VERY popular 2.5 issue though, worn camshaft drive gears. I've seen many 2.5's like this... very, very many.