The Sniper has its own ECU that is mounted in the throttle body. It uses the same basic software as the HP systems which is why there is a check box for progressive linkage.

From what I can figure, when you check the box the rear injectors are turned off until the TPS % is hit. The problem is, the AE tables are not modified when you switch to progressive so now you get about 2x the fuel that you need below the cut in point. (30% TPS used to open up all four throttle blades 30% but not it only opens the front throttle blades 30%.)

I reduced the AE and that solved the bog off idle. So now it runs okay with progressive linkage but I wouldn't say it runs perfect. There are still some spikes in the AFR plot and off idle performance is a little iffy.

The issue that the Holley guy has is that on a street car the rear injectors will be turned off most of the time since you can do a lot of street driving without ever needing more than 30% throttle position. I think they are worried about the injector life if it just sits there and doesn't do anything.

Since progressive linkage is unsupported on the Sniper he basically told me I was on my own. He said they don't recommend it, it shouldn't be used and it is unsupported. But he also said it makes sense to have progressive throttle on cars like mine with a large engine so perhaps they'll add the feature (and support it) sometime down the road.