Join Date: May 2011
Location: Frederick MD.
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Early year 7.3's didn't have a wastgate. They do have an exhaust backpressure valve that is used to choke up the exhaust to warm the engine up in cold weather. Sometimes this will hang up and cause it to run poorly.
Does it sound like an exhaust leak by the firewall? These trucks are notorious for the turbo up pipes to leak, causing low boost and low power. It's usually most noticable when under load like pulling a hill. Get under the truck and take a flashlight and look at the pipes that go from the manifolds to the turbo. Up near the turbo y pipe is where they will leak at. Look for signs of black soot around them.
If these pipes are leaking badly then it won't give the turbo enough exhaust pressure to work properly, causing low power.