Who says hot weather is bad for your cars performance,had a little play on my way home from work hitting 21psi every time i floored it and holding at 20psi till i either ran out of road or speed getting a bit naughty(70mph btw).
The car feels awesome 
Check the altitude correction with vagcom,
Because if the altitude sensor reading wrong the ecu can offset the load/ms, reducing the boost or adding the boost. I want to find out at what atmospheric pressure there is not offset. then all realted maps can be mapped out to one value, the maps am looking at only scale to just under 1000mb
I have noticed a few cars with this sensor causing boost issues, so if I can apply a patch in the map it will sort this unseen hardware issues out.
Nick