I would be surprised if you didn't see 300.
S15 Injectors are reaching their head (duty) @ 14PSI. Putting more boost is just going to push the injectors over the edge.
I would have used 555's, but I couldn't find any up for sale. They were all sold very quick.
Response, well there is no lag basically. The E85 has made the throttle response for all intensive purposes, instant.
It's growing some real balls in the top end now.