I've been following this thread with much interest being a former 718 2.5t owner, latterly with the superb 718 2.5t GTS.
Heat dissipation on the Cayman platform is a major issue with the turbo engines, especially when tuned to their true potential. As Jeff rightly pointed out in an earlier post, McLaren, Ferrari, etc, have no such problems being designed for turbo engines from the outset.
Tuning turbo engines is the easy bit, it's dealing with the engine compartment heat build-up and extraction that's the more challenging problem. In my experience when tracking my 718 2.5t GTS I never had any power back-off issues, even on the few warmer track days I encountered.
Taking the opportunity to dispel the widely perceived view regarding turbo lag, I can unreservedly confirm that using manual shift PDK in a well practiced manner on track, absolutely zero turbo lag is evident. My 718 2.5t GTS posted a 58.76 second lap time at Knockhill in August 2019. The power delivery and flow from the turbo was smooth, instantaneous, and linear. In my humble opinion, thanks to variable vane technology working in concert with variable cam timing, turbo lag has been completely eliminated given an experienced approach to driving techniques.
As R&T so aptly put it when testing the 718 Cayman 2.5t GTS......
According to R&T -
The Cayman GTS’s most notable trait, compared with its six-cylinder predecessor, is its immediate, abundant, and unrelenting thrust.
Brian