Speedo affect tuning?

[GTS]

So I know it's going to affect the shifting if the speedo is off etc. But does the speedo itself affect your fueling as well? Reason I ask is I put a 120mph lightning speedo in my truck the other day and now it seems my programs don't fuel as heavily as they used to. Most of the programs would smoke a good bit and now they don't do more than just a light haze. When I crank it up to my full on nitrous program it still blacks out 4 lanes of freeway but the rest of the programs are much weaker than usual. It seemed to happen at the same time I swapped speedos so I'm thinking this is the culprit.

Bill if you read this have you done any tuning on the lightnings? And if so is there something with the speedo that would affect my tuning on my diesel?