I have a Mk1 1992 1.6 with an M45 supercharger (fitted by Mazdaspeed nearly 20 years ago!). No intercooler. Standard injectors. Standard ECU, no piggy-back, not even MSD boost timing unit or Bipes ACU, so timing 8 degrees BTDC @ 950rpm.
However, it seems that I am getting the same problem as you - when cold, the idle bounces for a couple of minutes and then settles down.
I have also reset my base idle, checked for fault codes, cleaned and checked the PCV valve, replaced the plugs, HT leads and air filter. Put the car on a rolling road last week and the fueling is fine and peak power is a healthy 178 bhp at the flywheel.
I will be replacing my oxygen sensor this week and was then, just like you, considering the MAF, coil pack, engine coolant temperature sensor, etc.
Please let me know if you find out the cause of the bouncing idle - I will do likewise!