is this a converter problem?

[87gninpa]

When letting off the throttle quickly the car seems to want to die, and sometimes does, but then quickly goes bacjk to normal. i thought at frist it was an iac motor problem, but i replaced it with a new GM unit and have it and the tps properly adjusted. someone tols me it may be relate to the converter, could this be true? if so, any clues on how to fix it? also, the converter is a pretty new stock unit with less than 30k on it