need advice before i proceed - whipple 5.3 truck

[2000_SS]

A guy brought me his '99 silverado with a whipple on its 5.3. this truck is 100% bone stock, minus the whipple. He was complaining about the truck feeling slow and barely running with a "stock hemi truck." He wanted me to look at it and see if i could do anything.

This setup is new to me. The only thing i see under the hood that doesn't belong besides the blower, is a black controller box of some sort that splices into the MAF and (i assume) MAP sensor to control two extra injectors. The tune file in the truck is stock, or at least almost stock compared the the alleged stock '99 file i pulled from the repository. i'll post it below.

I took it for a drive. it wasn't impressive, but didn't feel like a complete dog either. there was some knock retard. i'm guessing this might be burst knock or false knock, but can't be sure. i didn't check to see what plugs were in it. according to the gauge on the dash, it looked like it made 6psi of boost. Fuel trims aren't great, it needs tuned for sure.

I'm just curious how to proceed here. Should i flash a custom OS? i'm fairly certain it has the stock MAP in it. It was pegged at 104kpa in the log, injector duty cycle was through the roof. i'm sort of confused because of the controller box/extra injectors and stock tune file. If i go ahead and start calibrating, will my work interfere with whatever that driver box is doing? i dont know how that thing works in conjunction with the stock vcm. It still has torque management and everything in it.

[edcmat-l1]

First thing, is do a little research, and find out what injectors are in it. Second thing, is pull the "box" and add on injectors out of it. Then tune it like normal.

PS, I would do a 2 bar tune.

[2000_SS]

I was thinking the same thing, thanks. I was hoping for a less-costly route because i know the guy doesn't want to spend a ton on making it right and also doesn't intend on keeping the truck.

It has stock injectors. It appears that it still has every single part GM put on it in the first place except a different intake tract for the blower.