so I recently had my tct upgraded to the Ballade sports tct so first lets rule that out as the problem.
second I had a valve adjustment done roughly 5k miles ago by Ballade sports during the same time as the tct install.

car currently has 110k miles 2002 ap1
bought with 103k

maintenance done after buying
upgraded tct
valve adjustment
ap1 retainers
iac cleaned and map whack +zip tied
use castrol gtx high mileage
mobile 1 high performance filter
last changes 1000 miles ago
check oil level during every fuel
ecu idle relearn
all fluids changed
215 compression rating on all 5 cylinders

problem
so I when the engine is still warming up but good enough to drive (just reached 3 bars) whenever I slow down to a stop light and it idles for about 10 seconds or more I hear a rattle that comes out of my engine bay . from the interior it sounds its coming near the passenger side... but then again I'm not 100% sure.
sound goes away after I drive then next stop light for more then 10s it will come back

I checked to see whether the header heat shield was cracked but I honestly was not able to tell.

the noise itself sounds pretty dull not really high pitched metal like a heat shield rattling

anyone have an idea?

 

took a closer look sounds like its coming from the header's heat shield. but it only comes up if my idle dips to 3 bars then it stops again from 4-5 bars. sounds like just a rattling piece of metal but its not like super heavy vibrations its just really dull sounding. is that what the header heat shield is supposed to sound like? it was too hot for me to check so im waiting for it to cool down

 

How were you planning on checking? If you can get it to rattle while parked with the hood up, you can just poke around with a long socket extension or screwdriver to feel for the rattle.