So this will really only pertain to a select few people here, but any reasonable input is appreciated!

2008 civic si
mods:
PLM header
rick specd short ram
vibrant cat back
j35 tb
fp tuned by vit

here's whats happening:

when slowing down and coming to a stop i like to put the car in neutral and coast. when the rpm drops, it drops down to 3-500 rpm then bounces back up to 1000, and settles to like 800 (standard idle). This started happening last year, only when it was cold out. then it started happening when it was cold and/or wet. now it happens every damn time i drive. I can't figure out what could be causing it. I did have my plugs changed a few months ago but it just recently started doing it all the time (like, last week).

anyone have a similar issue? the car never dies out or even feels like it wants to, it just shakes until idle comes back up and it stays there. Seems to happen worse when i go into neutral above 3500 rpm. its more annoying than anything.

so, ideas? vacuum leak? sensor issue? can anyone here read a flashpro datalog enough to see if there is an actual tuning issue?

thanks!