Turbo question

I just bought a new truck, 03 f250, and the dealership I bought it from told me they put a bigger turbo on for the previous owner. I'm ordering my custom tunes soon, and needed to know what turbo I have. I'm thinking it's a powermax because of how it lags really bad till about 2500 rpms, but I'm not sure. Is there a easy way to tell what I have? I assume I would just measure something, but I don't know what measurements I'm looking for.

Pull the intake off of the front of the turbo and measure where it goes into the compressor wheel. If I remember correctly the Stocker is 58mm, so anything bigger is an upgrade.

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