Nah mate your TD42 will very happily boost to 15 all day mate. The standard Actuator is set at around 10psi and MTQ preset theirs at 11 but fitting a variable Boost controller will allow you to wind up the boost to something more reasonable at about 14 to16psi and have a very happy car all day.

As you explain and as noted in my previous post your temps get better with a gear change and that because your getting out of the Bog Zone which is low boost below 2200rpm. At those revs you turbo is not quite spooling enough and looking for max fuel to boost but not getting enough so tries harder and gets hot. Increase the revs or back off the throttle slightly and up the boost and you will be blown away.

Not enough Boost is clearly the problem as your temps are consistently too much fuel. Match the fuel to the boost and it will improve dramatically