get an Ls1 
j/k but the difference in power could be from the air differences even tho last saturday was pretty coool outside. also i’ve heard you can make differences in power just from tire pressure or the way the car is strapped down on the dyno. I think you just need bit bigger turbo and better piping to flow more air for that motor. 250+whp should be easily reached and that will be afun car. ever run it at the track as is?