Details: 88 P/U, 305, 2X4, auto, 2nd motor and trany.
The truck has 247,000 miles on it. The second motor is a Jasper with 98,000 and trany is a Jasper with 75,000. Tune up about 3,000 miles ago and new fuel pump/filter. Truck was running bad and loud so I took it to a shop (small but honest) and they replaced drivers side ex manifold and catalytic converter that was very blocked. Also checked compression (155 in each cylinder) adjusted valves and timing. Truck is quiet again but lacks power and has some major flat spots in acceleration mainly on low rpm. The engine also seems rougher running overall. The shop isn't shure what to look for. I was wondering if power problrms and flat spots could be internal (mayby result of major back pressure and heat from blocked converter) or electrical/tuneup related?