Wouldent be glowing red, But i would think a temp gun on a punched cat would be alot cooler then a Complied Cat. The CAT in theroy should also be hotter then the rest of the piping back to the exit.
I would also think the only way you'd get pinched is a Road side inspection bay......Stand DECCA emmisions test you would just swap to a std cat, Though even then they would only test for what the Notice is for, Though i vaguely remember him checking the temp of my cat