Nissan Repair: 89 nissan A/T, 2WD truck, excessive fuel, optical pickup

Question
I have a truck were I've replaced the following:
Rebuilt TBI(gaskets/O rings)
New distributor/rotor
New Alternator
New EGR
New spark plugs
I have checked both ingition coils and tried to retime the engine but I am unable to adjust it(tried in Drive, not Park). I then did it by "sound". It starts and idles(high I think) and now the tachometer on the instrument panel does not work. It has poor performance under acceleration and uses excessive fuel. I have also attempted to adjust the carb(to no avail)and I'm at the end of my patience and out of ideas...Any ideas/sugesstions are appeciated.

Answer
Steve,

Remove the distributor and take the ahaft off and the cover below and check for oil on the optical pickup.  If there is oil replace the distributor.  When you said the tach did not work that led me to think the distributor has the internal seal fail and that is screwing up the ignition on the truck.