How do i know if my used car has a performance chip on the ECU with out disassembling the ecu?

i have a 98 jetta vr6 glx i did a little experiment with fuel octanes, i tried 89 octane than i tried 97 octane and it seemed my car loved every drop of 97 Oct….... more than the 89 is there any way to for sure know if i have a chip with out plugging it in or….such activity…? now there is a little sticker on the gas intake door that says: unleaded 89 octane only. but that’s a factory sticker. thanks much!