I am using the GM connect and cruise pcm. Is HP tuner the way to go? Are there others? What other stuff will it do?

Get with a really good tuner and they can make that trans work awesome with HPT. Just make sure they have experience with tranny tuning.

HP Tuners is your only option with stock ecu. Where in BC are you again?

On the island, Port Alberni

Im not super familiar that far west, You could try calling the guys at Gen III Speed in Kelowna and see if they can help you out or recommend a shop closer your way.

Spent the day researching HP tuners. I might pop for it as it kind of matches my back ground and we are a little remote here from professional tuners. From what I can see I would need to buy a MPVI2 and two credits. HP tuners don't make it straight forward on their site list showing what is supported as far as crate engines go. Mine is a LT4 8L90 which I purchased new in Sept. 2019. (not on their list) but they support the new LT5 so I assume they do the LT4 8L90?

So I popped for the HP tuners and the first thing I was going to do was adjust the tire/ gear ratio to bring up my cruise rpm (even though I am in the middle of GM's recommendations). Pretty disappointed to find the TCM is locked. Yes I understand I could send it to HPT, WTF! Anyone else running the 8L90 transmission have feedback on their cruise rpm's?

So truck has been sleeping all winter and took it out a couple of days ago. Drove fine until I gave it significant gas and it rev'd then not several times. Came home and has check engine light on PO700 which is a transmission code and P18C2 pending. Also am told shifter positions are PRNDM. Mine and at least 2 others have one more detent, PRNDM? Heard it could be PRNDML?

Have you called GM or talked with a GM performance dealer about it?

I chatted with a GM performance tech today. Says delete codes and see what happens. I asked about the extra shifter detent (2 of my buddies have same) and all I could get from him was don't use it.