Ford Repair: 1995 E350 (Class-C RV) 7.5L/460CID Idle good, smooth when cold, stumbles/hesitation under load, exhaust leaks, manifold gaskets

Question
Hello,

 Have read your past responses and thank you for contributing to us Shade Tree group out here.  I have a 1995 E350 Van (running gear for RV) that I just completed installing copper exhaust manifold gaskets on to fix the constant manifold exhaust leaks - all fixed now.  I have a problem with the truck stumbling/hesitation/missing when under load and warmed up.  Will not stumble at low or high idle in N or P and only stumbles in D or R or when accelerating after warm.  I was careful during the work and only scarred my knuckles and took my time to do the job.  I did have to have to move the fuel line bracket and lines during this and did unplug some vacuum lines but reconnected them upon completion.  It did not do this prior to repair job and have not checked any fault codes.  I am thinking that either I have an unconnected vacuum hose in the engine bay somewhere or either cracked a sparkplug insulator when working on the manifolds etc.  I checked the plug wires but may have a loose one or something affected by heat once warm.

 I did unhook the EGR hoses from the manifolds and used anti-seize compound to reconnect at the end.  Any ideas?

  Thanks,

 John
 Springfield, VA

Answer
Hello John, I think you are on the right track, you'll have to 1st check for a vacuum leak(use a carb cleaner or a brake cleaner to spray around the intake while the engine is running to see if there is a rpm change). If that is all ok then checkthe spark plugs and wires. Thanks Tony