Since none of us are able to see for ourselves....take into consideration, that just maybe your expectations on just how powerful it should be, could be higher than what it actually is.
This doesn't sound like the case, but again...we can only speculate without actually being able to take it for a ride ourselves.
You do have a few "bolt-on" mods, but for the most part, sounds like a stock motor.
You know anyone that has a K5 you could take for a spin, to compare?