86 Lincoln with 302 v8 with HO Mustang engine won't take gas & shuts off.

Put my 86 Lincoln in garage to fix serious oil leak at the lower intake.
Replaced all gaskets & seals and thermostat and pcv valve. Upon putting
the car back together, mechanic can not get the car to take gas. When you
try to give the car throttle, it resists and will shut off. If you gingerly, ever so
easily apply throttle, sometimes luckily the car will crank and idle fine. But
when you try to give it throttle it wants to resist and shut off. So the
mechanic tore the car down and for 2nd time, replaced all gaskets and
seals. Put the car back together with NO CHANGE. Pressure test shows
the fuel pump is good. The plugs and wires are new and test fine. Test on
injectors shows to be good. What could be the problem? Does anyone
have any idea on what we should check next,cause we are about out of
ideas.  Thank you. David Hedgecock