It’s always better to test something by itself for the first time, especially if you are testing a putative.
If I were speaking from the store’s POV, I’d suggest you try p83 alone so we can gather more information about the unknown putative.
It’s more than likely that the combination might give you a heightened response. But if you don’t know what the original response is, how will you know if you are getting a heightened response, let alone which response is being heightened?
Mad Tater once said he was at a gym on the stepper wearing this 83/IFM combo. all machines were empty, yet 2 girls chose the steppers on either side of him!