I currently running a 502 EFI with a M1SC, I'm considering changing the pulley from a 4.25 to 4.0. Should I plan on gettnig the ECM re-programmed? and any idea of what type of boost increase I will see?

Below are the numbers from last dyno pull:
rpm: 5200
hp: 709
oil pressure: 81.7
fuel pressure: 73.9

thanks

More air will need more fuel .

What year ecu/mefi do you have?

What boost was that at? i would say you will need to change the program on the ecm. i would also check and make sure you are under the max rpm of the procharger

1996 ECM and running between 4-5lbs of boost. Motor was freshened up 2 years ago.

I think ArticFriends asked the magic question. A 1996 is probably a MEFI 1 and I don't believe they recognize boost (no boost compensation table). So, fuel is controlled only by rpm at anything over 100kpa. A MEFI 3 would be a great upgrade for tunability.

How far did you pull to, max RPM ?

You got some good HP for that boost. If the ecm is set up for the stock motor I think you will need to do some reprograming if you go for more boost.

are you running the stock 48# injectors at 74# of rail pressure?

thats a lot of HP for that setup....unless this is like passtime and not being told everything...