Comparing humans and cars ? Seriously ? I don't think this example is relevant here. I never said they struggle to breathe. What I said was that due to reduced density and hence rarity of oxygen which is sensed by MAF & O2 sensors, the Ecu based on these readings adjusts the fuel map so that the stoichiometric ratio is maintained. The Ecu will try to maintain this ratio in order to keep the performance and emissions optimum. The ECU also uses the IAT as intake temperature too plays a crucial role and is a critical parameter. I beg to differ with your second contention. The maximum ambient temperature is what, 40-48c in our conditions ? I am dead sure such temperatures are negligible when we talk about metals expanding when subjected to heat. Melting point of most metals,the ones commonly used in automobiles is a good enough testimony to this. Also if the metal components expand as to what you are claiming, how would the gaps increase ? Shouldn't they theoretically reduce ? Why would the fuel pumps pumping capability reduce ? 'It can cause similar problems with multiple components to bring down the overall engine power' --> Care to explain how and why ? Could you explain why only turbocharged engines ?