Is it a clogged cat?
Replaced fuel pump/line. Replaced plugs,
wires, cap, rotor. Truck misses at and over
2750 rpm. Fuel pressure is good. Timing
cover gasket let go during a running test.
Lead me to exhaust. Hissing noise was
present. Fixed donut gasket. Noise is still
there. Think it's the cat ,but I don't want to
spend $300 without another opinion.