MAP and which map it uses

[Lawn Choppers]

I bought a truck with a tune in it. It is a 2005 LLY they didn't complete the egr delete and thanks to you guys I was able to.
Now I am looking at the tunes and the efi customs they only change mapC is that because MAP is always high enough to use mapC ?
I am getting ready to attempt my first changes in the tune on a 2004 LLY 3500 dump and want to keep it mild just gain more torque. Can I do this with lengthening the pulse and advancing the timing a little or would variable vane be something I should mess with ?
Any help would be appreciated I am new at this but have a lot of experience in working on duramax's (in the last month 3 sets of head gaskets 2 sets of injectors and new injector lines all on different trucks)

[THEFERMANATOR]

Many tuners only mess with map c which is basically used below around 5500 feet of elevation and lower. This has caused many issues for some. Other tuners only modify table C, and then change the altitude tables so they stay in table C all the time. Myself I modify each table set individually. To me I fell it helps out to deal with elevation changes. Instead of using a 1 size fits all approach, I maintain the OEM functionality.

[Lawn Choppers]

That makes a lot of sense. I thought it was all engine temperature controlled. I want to try changing the tune in our 4500 topkick I'm hoping it isn't locked somehow. I know before when we were using Edge they didnt have one for the 3500 or 4500. Just like to give it a little more torque.
Thanks for the help...