Check the electrical.....as said over and over in earlier posts. That and the exhaust are really the only big fabrication items.

Check to make sure all the wire connections are soldered and covered with heat shrink plastic....not crimp connectors....crimp connectors will fail eventually.

Make sure he has both O2 sensors in the exhuast.

Take an ODB-II tester with you (or drive the truck to an parts store like Advance Auto, they will do it for you) and hook it up...check for ECU recognition and codes.

Make sure he didn't do a hack job on the exhuast either....good welds and that it is supported properly.

Look closely under the hood and make sure everything was relocated and/or installed securely' all wires are tape wrapped and securly tied down. Make sure he has the correct EVAP box (should be a square-ish black box) and, that it is hooked up.

Other than that, make sure everything works...tach, gauges...the motor idles around 750 and is smooth....there is no reason the truck shouldn't run like it came from the factory with that motor.

If the guy did a nice job, you'll love the truck....I love my 3.4L '94 4Runner.