What cam did you use?? It is important to get a computer compatable cam. It's a tan/blk stripe wire with a disconnect. It's usually hanging out of the main harness under the brake booster. Disconnect, set base timing and reconnect. But you can ONLY set base timing. The rest is done by the computer.
On a side note, We had a problem with my buddies 89. no codes put out, but had very little power. The engine had some mild noises inside. valve train noise(it was tired) But the noises were enough to trigger the knock sensor and kept retarding the timing. Does your engine make ANY noises?? I have heard that even running double rollor timing chains can make enough noise to set it off. Factory chains sets have nylon gears to keep noise down. Put a timing light on it, rev the engine up a bit. See were the timing goes to. Also, on the starter side of the block is where the knock sensor is. While the RPM's are up, tap the side of the block and see if the timing jumps back. (tests the sensor.)