I was recently given guidance to lower Cyl 2 temps to make the CHT grouping tighter and improve overall power options, particularly in climb.  The suggestion and demonstrated method was to cut a hole in the front wall of the oil cooler airbox to encourage air to get around the aft side of Cyl 2, and add a box to the opening (extending into the airbox in front of the oil cooler) so the ram air for the cylinder does not mix with the air heading through the oil cooler.  With the engine installed, this is a tough modification in a narrowed space, and my fingers/knuckles would take a beating if I tried this without removing the oil cooler en bloc from the back side of the engine.

Instead, I tried something different and created an alumimum bilayered flap/scoop coming off the oil cooler door, anchored via the same three oil cooler door hinge screws, to catch incoming air and divert more to the Cyl 2 aft side.

I should have taken a picture before I zipped up the cowl...sorry.  If there's an interest, I'll send it as an addendum.

The pre-installation temps were (level cruise):

Cyl 1   368     340

Cyl 2   394     364     Cyl 2 running hottest, a problem with full power climbs.

Cyl 3   356     332

Cyl 4   356     331

Cyl 5   346     331

Cyl 6   326     309

Diff HiLo       (68)    (55)

After installation of oil cooler door scoop (level cruise):

Cyl 1   339     334     346
Cyl 2        352     346     356
Cyl 3        330     328     340
Cyl 4        328     323     340
Cyl 5        330     330     337
Cyl 6        309     307     318

Diff HiLo       (43)    (39)    (38)

No change in oil temps observed.  Power settings were not matched pre- and post-.

I do not have climb out data yet, when the power settigns and temps are much higher and the airspeed is lower.

Looks like CHT#2 is a bit cooler with this simple mod.  Nicely, the more the oil door is open, the more the hinged aluminum piece takes a diverting bite of incoming rushing air.