^^^ this! Moreover, the OP lives in Houston. Get a Costco membership. They have top tier fuel and their premium gas prices are normally what regular gas costs at other (non-warehouse) stores. Plus if you get a Costco Visa, you get 4% back when purchasing Costco gas. The gas savings alone pays for my membership.
I was just about to say that. Here in OH, Costco premium is the same price as everyone else’s regular. They add a good amount of detergents too. Allegedly, a GM tech instructor I used to know said they were having great luck with it in DI engines. You can also buy Techron in there which I would run every 5k. The brochure and Ford’s website both recommend 91+ for the 3.5HO. With the Texas heat and amount of boost the engine takes, I wouldn’t run anything else. My 5.0L in my Mustang is rated to run on 87, but I never have. Honestly, during the Obama Presidency when he was searching for fuel economy solutions, there was a push from all the auto manufacturers to make 93 octane standard. I don’t know why that never happened. There isn’t a single gas engine out there that couldn’t benefit from a tune to run on higher octane.
As for your undercoating, I recommend a product called Woolwax. I spray all my winter vehicles with it every Fall and it seems to really help. Up here, with all the corrosive crap they dump on the roads, you can’t spray enough. It’s a lanolin based formula and will creep around when it gets warm.
