Hey guys. I have a 2005 F350 Crew Cab SRW. Not to many mods done. ARP's, all new injectors (stock), Sinister EGR delete, (not just the plate, full cooler removal), STC HPOP fitting, dummy plugs, oil cooler, AFE stage 2 cold air, AFE 4" turbo back. That being said, i also have a SCT X3 with custom tunes from Eric at innovative. I run the Xtreme Street as my daily. With the tune ON I have a good 3-6 second lag time from drive or park into reverse. I take the tune OFF, wait 10 min or so, driving or not, at the shift lag goes away. Does anyone have any ideas? I just dumped 9k into thing and I'm tapped out! Its just one thing after another! Standard 6.0, i know. Thanks for your time guys, hope someone can help. -Adam

 

Adam, I would seriously suspect the tune/tuner. If you read down a couple of posts to mine, about my 5r110, you will see I have/had similar issues, except mine is stock.
The transmission line pressure runs, idle/neutral around 50 - 80 psi, and when you shift it to drive it bumps it up to 150(ish) and even higher in reverse.
So... if you are driving it like that you will be running very low line pressures. It is this line pressure that engages your auto trans clutches. If it is low for even a short time, it will tear itself apart - quick.
To check it, you will need an oil pressure gauge that will read a minimum of 300 psi with a 1/8 pipe fitting. Screw it in to the plug threads, just in front of the shift arm on the side of the tranny case. It should spike as soon as you put it in gear.
I read in another forum about a VERY similar problem with an SCT tuner.