Spray carb cleaner around your intake system.

This has what has been done.... I've replaced the MAF, throttle body with one I knew were working fine from other similar cars own, I've replaced the PCV..... I've blown smoke thru the vacuum with no signs it is coming out anywhere, I've spayed carb spray..... I still have a LTFT of 25 and STFT of 16 at idle, and the MIL is coming on with a P0507.... this is driving me nuts... I wish I could find the problem....

V6 or V8?? If the V6 is it super charged?

3800 Naturally Aspirated.

How old is the intake plenum/gaskets?

Mike ^^^^^ has a good question. If the fuel trims come down with higher rpm it'* likely the LIM needs to be sealed.

Brand new gaskets on those.... no signs of leaking there with smoke machine and I've even sprayed carb spray around the area and no change in RPMs...... this is driving me bananas.... all the things that I've dealt with before with this code has an immediate fix..... all I've done this time is not remedying the problem....

Yes, but those plenums can still crack if they are torqued wrong. If it'* not too much trouble, try to block off the port for the EGR and recheck your LTFT'*.

Would not a smoke machine have shown if there was a crack in metal?

If you could close all of your intake valves, you will never know.