Heat affects them hugely. Mine pulls soooo much power back when it's over about 30 degrees. At 40 degrees I don't even bother driving hard it's that slow plus it's probably terrible for the car in general. At 40 degrees I can have my foot flat in any gear and keep traction (have semi slicks though which would be nice and sticky cos of the heat). At 20 degrees or less it will just spin through first and second with flat foot
Having a bigger intercooler does help I notice a bit of power comes back if I go for a drive at 100kmh or whatever on freeway and get heaps of air through the cooler but slow speeds it stays hot. Didn't notice that with the stock cooler, when it was hot it was slow and didn't get power back until the outside temperature dropped.