Changing Injectors (What to do with PCM)

[cmerc]

I have Tuner CATS tuner program which I just got and I am totally new to PCM programing and I am looking for help with the following.
I am going to change my Injectors from 27# to Ford SVO 42#. What do I have to do to correct my PCM for the new Injectors.
Is it as simple as changing the Constant, if thatis so do I just put in 42# or is there some other calculation that has to be used such as fuel pressure.

[Fastbird]

What motor is this for, and why are you jumping all the way to 42's??? Question being, is it warranted??? That's a lot of fuel capability there.

[QWKWS6]

http://www.audiohelix.com/file go here for a spreadsheet that will calculate the numbers for you. I haven't used CATS so I don't know how it sets up for different injectors. LT1/LS1 edit uses a constant value, HP tuners makes you use the variables,(more precise and time consuming.)

[cmerc]

What motor is this for, and why are you jumping all the way to 42's??? Question being, is it warranted??? That's a lot of fuel capability there.

383 LT 550hp, It had 27# injectors and 65psi fuel pressure when I got it and was running way rich with the small injectors.