ChucksTL_RENAMED

Have a 00' TL and wanted to ask you guys if anyone knows why sometimes the 3.2 (mine anyway) will lope into an idle that shakes the car it is so low and then goes back to normal, then back again, like 700 to 450 and so on like it is going to stall. Been using 93 octane always and ocasional Techron gas treatment. Thanks!