I have a 2006 silverado that was stock with the 4.3 that has the return style fuel system, it is V8 swapped with a cam and bolt ons but have always had an idle issue and would run lean, I have the stock intake/fuel rail set up from a v8 obviously and it has the fuel pressure regulator on the side of the rail, no vacuum hose is hooked up to it and the vacuum port on the intake is plugged so no vacuum leak, do the V6 fuel pumps have the internal regulator in the fuel pump like the v8’s do or should I put a vacuum hose on the fuel pressure regulator to intake?

 

Have you ever actually checked the Fuel Pressure at the Rails?

If it's a vacuum Regulator then it needs the vacuum hooked up, that's a given. Pics would help.

Given 2003-up didn't have a Regulator on the Rails it would be wise to check pressure at the Rails unregulated, then with a vac line on the Regulator to see if there is a difference.

Next question in the mix is if the tune is actually right.

 

I’ll get some tomorrow, I don’t drive the truck much, I was more curious if the V6 trucks had a regulator built into the return line or in the pump, I’ll also be adding that vacuum line to see if any difference is made tomorrow

 

So I hooked a fuel pressure gauge up and without the regulator hooked up we have right at 57psi at all times even blipping the throttle and putting a load on it, if I hooked the vacuum line up to the regulator we are seeing 57psi and then when I blip the throttle it drops to about 45psi or so and then picks up about a second or two later to 57psi

 

If the pressure is not dropping as soon as you hook vacuum up to the regulator, then you have a problem. Those regulators are notorious for developing leaks in the diaphragm, but as old as it is, it could be anything.

 

With the stock regulator hooked up in idling at about 50-51 PSI, and if I blip the throttle it jumps to about 57-58, key on engine off it’s at about 57-58

 

That's right where it should be.