My general experience with Diablo chips are not positive, I seem to see too many "wierd" things happen.
Much of this may have to do with the "generic" setup on most of the chips. Since yours was dyno-tuned, it shouldn't be the issue though.
I'm assuming you are using the chip to override the O2 sensor code.
Please be aware that when you open up the exhaust, you WILL lose some torque as the back-pressure decreases. This is normal and you should see an increase in your HP numbers.

__________________
Uncle Sam
"What the hell is up with all the gauges?
Calling Captain Kirk, your ride awaits... Phasers on stun...."