Best thing a person can do is get some kind of scanner with advanced GM PIDs and monitor knock retard. If the PCM is retarding timing on 87 there is power and mileage to be gained with higher octane.
I like a ELM 327 device and OBD Link with GM Advanced upgrade.
This Bluetooth ELM327 device and a smart phone or tablet with OBD Link with GM Advanced update has not let me down. I also use it for my 8.1 99 Tahoe, my Nissan and Inifiniti. Downloaded the Nissan/Infiniti advanced stuff too. Can look at all the modules, read and clear codes, etc. This will let you adjust the Vortec distributor CMR as well without having to take it to a shop.
https://www.amazon.com/OBDLink-Blue...17a-1387-4dae-bb74-9da8fe434220&tag=cb-osp-20
Actually I don't even have to use a phone or tablet any longer. I have a 10" touch screen head unit in the Express that links directly to the Elm 327 device that stays plugged into the OBD2 port. I have a dash display built on the app that has a tach, long term fuel trims, commanded air/fuel ratio, knock retard, instant fuel economy, and trans temp. You can monitor practically anything in the OBD2 datastream. All have adjustable warning points. Hands free bluetooth calling and navigation maps.
http://vi.raptor.ebaydesc.com/ws/eB...4&pm=1&ds=0&t=1605833972000&ver=0&cspheader=1
My next additions are going to be the S10 steering wheel controls, backup camera, and tire pressure sensors.
For a tuner person that normally datalogs with HP Tuners its the coolest interior upgrade I have made to my 97 and it was less than $300.