it feels like a complete shutdown for a half second, then back to normal. only when coasting in gear

monitored the o2 readings. directly after the pulse the o2 voltage drops to 0.00 or very close to it

Ok. The only thing that will cause the O2'* to drop to 0.00 volts would be a loss of fuel (IE: injectors shut off). This can happen in Decel Fuel Cutoff mode; but can also happen if you have a crank position sensor going bad. Where you on the gas (throttle) at all during this period or was this occuring durning a decel?

-ryan

absoulutly only occurs when my foot is off the gas. never under pressure

going to swap PROMs and see if it changes