Congrats on your new purchase MH1 and welcome to the forums. I don't recall seeing a pick of your new ride, if you havent posted it in the V92 TC thread under the V92 forum.
My take is what the dealer has in his computer is going to be the latest from Ma. Maintenane instruction manuals will always have the flaw of not getting an update or someone that was supposed to validate it, missed it and it is not cost effective to correct. The -6 being hotter makes perfect sense allowing better use of 89 octane fuel (as discussed in another thread that almost got drawn out) over the 91/92 which is going to provide better engine performance on down the road.
As I understand the Freedom engine, one of Ma Vics selling points was keeping things simple such as the freedom V92. If you were speaking of the previous generation engine (01 and back), that could be a whole differnt story I would think but since your 2002 and my 2004 are the same basic powerplant, I can understand why the dealer has it as a superseded. As for the plugs costing 1/3 less at the Auto parts, I just chock it up to working with my dealer and keeping my Vic business in house. I pick up plugs when I am there for something else so I didnt spend the gas going to the auto store... lol.. Of course, I like my local dealership, good group of guys and it usually comes out in the wash. Now if pricing was 30% on something much larger, battery or something I would ask him for a better price.
On a side note, about using 91 Octane (as I said, I stumbled on that discussion qouting something from the owners manual as well and wound up getting educated a bit) I think you will be quite impressed switching to 89 as well as your engine performing better with less carbon build up. I picked up about 4 MPG on the last two tanks and I have not been that lean on the right wrist either. No pinging, just flat better performance. Our temps up here around high 80s to mid 90s. Of course if you started pinging, go back to the 91/92.
Just my 2 cents. Hope it helps!
2011 White Vision - Nuvi 550, Lowers, Lloydz 2nd filter, Vic perf filter, CB/Icom, 96 Brake LED's, Clear Signal lens/Switchbacks, VIC Hwy Pegs, Stebel Horn, 7Jurock 15" Shield, PCV, Lloyd ATS and Variable intake, Ness honkers
2004 V92 TC - S1 flash, level 1 slip-on, Ness big sucker K&N, ISO Grips, 4x1.5 Highway Hawg Risers, extra chrome (never too much), JM 2k CB 4' antena, Mustang seat, HD Front TS & Lowers, OD Pulley
Retired Navy SCPO