99 FXD 88c.i. carbuerated, stage 1 air cleaner, no other mods.
when i twist the throttle hard, it wants to bog down for a full second, maybe 2, then jump RPMs, enough to jerk me back on bike.
when i'm decelerating, its backfires thru the exhaust.
Ive ran a can of carb cleaner thru, plugs are brand new NGK, and wires are in good shape.
where do I go from here?

 

Welcome from Hampton Roads Virginia. If it is lean and sounds like it is, either the accelerator pump is not pumping a shot of fuel or your jets are stopped up. Running carb cleaner thru diluted with fuel does little to nothing. And do not even think of running it straight since it will destroy the rubber and such in carb. A decelerating backfires thru the exhaust if the exhaust is open and you let the throttle back too fast is pretty normal. You may need to go thru carb.

 

I agree, time to pull out the carb and clean the jets and all the passage ways. Old gas?, bike sitting along time with old gas? If so, jets probably clogged. Especially the small holes in the low speed jet and the small holes on the emulsion tube. YD