rockpapernuke

I have a '99 K2500 suburban 5.7 that I bought a year ago with 84,000 miles on it. It burned oil like crazy and developed a rod knock. I bought a brand new L31 GM goodwrench long block crate engine from Pace performance that was matched to the VIN. Installed the engine with new fuel filter, cap, rotor, plugs and wires. Engine started right up and idled smoothly, no check engine lite, only smoked for a couple miles. I followed the GM break in procedure to a tee. It has been in for 150 miles. Now for the issue. I have worse performance than with the old engine. No bottom end power. Could the computer still be learning the new values? Any ideas?