17087194 is a negative backpressure EGR valve.
Port EGR valves use an EVRV (electronic vacuum regulator valve) solenoid.
A ported EGR system is different then a negative backpressure system. Your truck has a negative back pressure system.
Negative backpressure valves should hold vacuum with the engine off. When the engine is started the valve should bleed vacuum. The slightest pulse of pressure in the exhaust system will modulate recirculation (close the valve at least some). A good test for these is to put a hand vacuum pump on the EGR valve and apply vacuum with the engine off and it should hold vacuum. Leaving the vacuum on it, start the engine, and the valve should close.
The negative backpressure EGR has an internal air bleed that is held closed with a small spring when there is no backpressure. When the engine has exhaust backpressure, the small internal air bleed is open and vacuum cannot open the EGR.
Here is a site with a good illustration of a negative backpressure EGR valve.
http://shbox.com/1/EGR_valve.jpg
You should also inspect the vacuum hoses and make sure vacuum is getting to the solenoid that controls the EGR valve.
A comment about your headers:
Exhaust system backpressure can greatly effect the operation of the EGR valves on many vehicles. Modifying the exhaust system can effect how well the EGR works if it changes the pressure in the exhaust system. Exhaust back pressure (from a restricted converter) or no back pressure (from no converter or mufflers) can have an effect on how much the EGR opens.
Another comment I have about your truck:
Any time you install headers a heated O2 sensor should be installed on the vehicle.