Air Filter - or - not to filter the air ?

[olut]

Short description:
35-A with original Zenith, air filter attached last fall, worked well, no significant loss of power, did not run rich or lean, ambient temperature below 80s.

The past two days we have high summer with temperatures in the 90ies, all fine when engine is cold, but as soon as the baby is getting warm, engine wants to die when accelerating, backfires and stops misbehaving only at low RPM, adjustments on the GAV dont resolve the problem.

So I removed the air filter and all is perfect.

Reason: that carb is not "air balanced" to be used with an airfilter (like those in my other babies 76-A and 165-D), cold intake air has less volume than hot intake air, if there is a certain flow rate limit at the filter and this is been exceeded due the high intake air temperature (close at the exhaust flange), then the carb should mix rich, but backfiring is always an effect of lean mixture......
...sounds not realy logic, where is the error in my point of view ?
...any thoughts ??

Best Greetings from hot Vienna