This thing is a behemoth! It wants to blast and I have only seen it Rumble and Grumble with Desire to blast. It burns the ground up to 6-8ft.
James is right, Your delivery is low. Try that. Jump up with your injector lines. You may have some restrictions some way!
Heat it up with propane and Do like Adam did with a weed sprayer pumped up diesel?
While it's hot and running give one of the intakes a shot of diesel via bug / weed sprayer?
Are you feeding all three intakes? Yep! Just read that.
Yep this think wants to Whoopee it Up!
Ok the bug sprayer is low tech but may wake up the monster to tell what it can do!