What do you mean it's not as drivable? What kind of issues are you experiencing with it?
Yep, the first thing that I thought of was my turbo. So this really narrows down my choices to only 2, Pag Parts brushless which is $1795 and rated to handle 750 - 800 whp or Precision Raceworks Stage 4 (dual 450) which is $1400 and rated to handle 1000+ whp. Either way I'm spending over a grand.
The E5LM/BKS1000/veyron pump (Iroz/Innovate/PPT brushless kits) doesn't come with a check valve. Same issues you'd have if you upgraded to a 535, less restriction/more flow but you get weird pressure issues at startup sometimes, especially on e85. I'm working with Arnold to redo my lines with a high-flow in-line valve because it'll occasionally dip low enough to trigger a CEL (though pressure is always fine after it's running).
Stuff I'd say is fine for a racecar, not cool if you want to have someone else go drive your car without a bunch of warnings and explanations.
I don't know how reliable long-term using the OE controller retrofit is, I've been told the PM5 is the ideal solution but that's almost another grand on its own. Plus the battery drain seems excessive compared to the PM4. You get a lot more output than the OE controller can do though.
I had great luck running a PM4 + 2x450s on my last car, I would think you could just convert your current setup to run a second pump much more cheaply. I liked that much more than the Hobb's setup PR includes with their stage 4.