how are you making the determination that isopropylbenzylamine is being used as a cut? is it based exclusively on the nature of the experience? I don't think that's sufficient - after all set and setting still play a role as they always do in every case of drug usage - and there are plenty of people who report dysphoria from known good product (even on pharmaceutical amps too). In fact I would view becoming super paranoid/hyperstimulated as evidence towards
overusing methamphetamine rather than suggesting it being cut.
The activity of N-isopropylbenzylamine is still uncertain, although there is no evidence pointing to it being active at doses typical for meth or cutting agent. It's been around for a while too, and has been seen either sold as, or cut into, methamphetamine since at least 2007.
Some tests to help confirm:
N-iso does not respond to Marquis test like meth does (no color change, meth goes orange).
The melting point of methamp.HCl is below that of N-Iso.HCl - meth melts at 172-174C, N-iso.HCl at 190-193c.
Also, the GC/MS, NMR, IR spectra will all differ. GC/HPLC/TLC analysis will show the presence of N-iso very easily.
It is said that the hardness of N-isopropylbenzylamine crystals is lower than that of methamphetamine. (not hard to say with certainty)
I note that other alkylbenzylamines have been seized as meth mimics before, N-methylbenzylamine and N-ethylbenzylamine hydrochloride. And
there was a case in Japan of "meth" which was really a mixture of phenethylamine and N-iso.