Oops -- I got my languages mixed up! Pfui = AE 'phooey'.
I can't guarantee the accuracy of every point of information in the above citation. But at the least, "phooey" has not been 'gängig' for decades.
I was going by the claim of 'disgust'. Disgust can be mild or strong. All I can adjudge is how idiomatic a proposed translation is, e.g. is it obsolete? I can't tell the meaning of the German text. I have to leave it to others to determine the strength of the disgust of the Motorfeinde and to rank the various German expressions.
Things that invoke the core meaning of 'disgust' include ugly sights and smells (e.g., you step in dog shit), and certain actions like child abuse. As CM2DD noted, *these* are the things that elicit the noise 'eewwww!'.
I am supposing what the Motorfeinde object to are the exhaust gas, loud engines, and maybe reckless driving. You *can* also be disgusted by loud noise, or environmental degradation, but an old man in 1925 would not react to these things with an 'eewww!'.
A gentleman *might* have said the things CM2DD lists (that's what older literature would have had us believe). A working class man would probably have said, "goddamn fucking X!".
'Humbug' just means 'quatsch', and I seriously doubt that it has been in use in AE after 1950.
In AE since 1960 (that's my experience), 'tsk' is a genuine vocabulary item (although of course not pronounced quite like that). 'Pah', 'bah', 'tut-tut' are just spellings we see in older literature, and we suppose we have gathered their meanings from the contexts. 'Tsk' would be totally wrong because it is too mild to denote Feindlichkeit.