I have a 1988 Ranger STX with a 2.9l. Engine blew a piston. I purchased a used engine, and am kind of putting together an engine with the best components of the 2.9l engines I have.
On the driver's side of the original engine the exhaust manifold has a large plug on it. See photos. On the used 2.9 I purchased, no idea what year it was from, there is a rigid tube that goes up to the top of the intake manifold.

What is that tube for? Should I use my original intake manifold and "plugged" exhaust manifold, or use the intake and exhaust with the tube connected?

Thanks!

 

It's an EGR (exhaust gas recirculating) valve.
I would run your original setup.

 

Will do. Thanks.