70% duty cycle is too high. 50% +- 5% is ideal. Is the duty cycle fluctuating. At idle it should rise and fall. This rise and fall is a result of the ecu responding to the O2 sensor. If you are not seeing this rise and fall go to the o2 and pin test it. Use a DVOM and put your negative lead on the o2 ground not a body ground as I have been screwed this way before. (Rust build up between the O2 and the exhaust can cause a faulty ground to o2) Put your positive lead on the o2 signal wire. Now observe the graph produced it should sweep nicely up and down on a 5s view. Voltage should be between .2 to 1. If you are not seeing this or if the o2 does not respond with a spike to throttle snaps replace it.