I think car's cooling system is extremely good. Therefore, except for short intervals I wonder how much engine temp will vary. I've run my 986S,997S and 997TT in HOT weather, in stop-and-go with AC on and never noticed a difference; amazing considering what the plumbing looks like on these cars.
I thought about adding the center cooler but haven't really run into a temp issue with mine yet. It's really not necessary. I seem to always run roughly 175F on the coolant, and 200-225 on the oil temps.
- at constant cruising speeds of 170km/h (4000RPM) the needle is at 100
- when I was cruising at constant speeds of 210 km/h (5000RPM) the needle stays in between 100 and 110
-coolant temp always stuck at 80*C no matter what.
Mind you this was a constant cruising speeds throu8gh straights and corners. And not braking, accelerating, braking, accelerating... in the latter case the temps may be different.