Nissan Repair: 1986 nissan hardbody D21 w/ z24I lacks power, head gasket replacement, nissan hardbody

Question
When I first acquired the truck it ran pretty bad.  It hesitated badly and often backfired through the throttle body.  I replaced fuel filter.  No improvement.  Checked for vacuum leaks.  Nothing obviously wrong.  Finally replaced distributor cap.  Truck runs much smoother with no internal backfiring.  Still lacks power however.  Replaced all 8 plugs and all wires.  Had a problem with a wiring harness going up to the throttle body.  It had been  bumped while I replaced the PCV valve.  Caused the truck to start and then stop running immediately.  After I found out the cause I pushed the plug in as tight as I could although it was not apparent that the plug was very loose.  The truck runs continuously now.  However, these little four cylinders have decent pep when in good running order.  Although the vehicle has high mileage(200k+)I feel that it is a good core power train.  We just rebuilt the head and reseated the valves after a head gasket replacement.  The engine was in good shape internally.  Could my lack of power be due to the coils not up to par, or is it perhaps related to the problem with the wiring harnass up at the throttle body?

Answer
Check the mechanical timing since it the head was taken off to renew it.  That means you need to run it to top dead center and then check number one intake valve event to see that it is about to open.  Also, check the timing.  Bump it a degree and drive it.  Continue to advance a degree at a time until it pings and then back it off a couple of degrees.  Also, for more power and fuel economy put in a K&N airfilter and think about a Magnaflow muffler or other performance muffler to open up the exhaust.  Both of these will give you more power with economy.  Lastly, check the basics like the coils for output and the fuel pressure for proper pressure levels.