1986 non turbo power from 5 cyl only. # 5 cylinder (rt bank rear) only kicks in with addition of extra fuel from rear of upper plenum thru a vac port or thru air intake. has new plugs and rotor cap wires-egr good 160 psi compression new intake and plenum gaskets ck cam timing (almost perfect cam belt has very little strech) new # 5 injector. air flow mwter passed all tests. this vehicle has been looked at by 3 different known good techs (includung a nissan guy w/ 23 yrs ) it is popular choice that there must be a air leak effecting # 5 cyl only but no one can offer an anwser as to where. with # 5 cyl missing the o2 sensor pegs indicting high o2 and ecu responds rich to injectors(seems normal response) when adding carb spray or propane to rear of plenum #5 cyl picks up offere combustion o2 starts to swing rich/lean and car runs near perfect. vac will go to almost 22 in @ idle. when runinng on just 5 cylinders vac is still pretty high. A friend of mine and myself are debating as to whether we' lacking fuel and # 5 cyl is effected first or is there an air or vac leak or something which is not letting #5 get all it's fuel charge in to cylinder? spraying carb cleraner or using propane all around the engine does not reval any vac leaks on the out side. I do not believe ther's any fuel delievery problems press good filter clean ECU appears to do everything it should based on inputs. This has been one of the toughest drivabilty problems I've encounterd. Has any one had similar -if so what's the fix???