Sorry to disagree, but if it was a clogged filter the engine would die under higher rpm and acceleration, not under decelleration. The fuel demands are less under decelleration, allowing the filter to "catch up". I'd go wiggling cables while the engine is running, but watch out for the moving parts. I had a similar experience that ended up being from the negative battery clamp just sitting on the (new) battery post without being tightened. Another of my experiences with a "professional mechanic".
Another thing to consider is there may be a fuel kill switch in the event of collision that may be setting off due to the negative g-force under decelleration. I don't know if you have it, but maybe look into it.
D'mon