I don't know enough to do the math... here is my guess....I think the actual increase percentage wise from the intercooler will not be enough to harm an already turbocharged engine.... but only because I think the amount of cooling will result in tiny extra amounts of actual air entering the chamber... now, if I am wrong on that part... and lets say it were to get near 10 or 15 percent.. then I would be very worried about the rod strength and the bearings... all of this is from intuition/30 years of mechanicing/reading about engines.....
The squish area on these engines is very small...
One thing on the heat dissapation these already turboed engines have going for them is the oil squirter aimed at the bottom of the pistons... the non turbo 5 cyl does not have that....