Chevrolet Repair: 93 K Blazer problem, size blazer, mechanic shop

Question
I put a new engine (350) and tranny in my 93 full size Blazer and have had driveability problems ever since. It struggles and hesitates at low (up to 2000rpm) engine speed. I replaced all the emissions except the cat. I replaced the fuel injectors, filter and regulator. New wires, cap, rotor, vacum lines, etc. The one thing I have noticed is that the gauges frequently, but intermittently read falsely low (it did this before the engine swap). And... the engine runs bad when this is occuring. The voltage stays steady. What could be causing this? Alternator? Would these two problems be related?

Thanks for any advice you might have!  

Answer
my brain hurts.. gremlins, you got gremlins... and i aint got any gremiln killer left.. get aht thing into a shop and fast.  sorry i cant be of more help, that sounds way too wierd and and get it into a mechanic shop and have them go over it, that would be the best thing to do for now.
sorry.