Limp Mode??

Here's the short of the long, 04 Titan SE Crew 5.6l with TB spacer and volant cold air. 101k. Truck ran great when bought. For a month.. started stalling out a lot. "mechanic" the dealer sent us to Saud it was o2 sensors and a bad relay.. Didn't say what, but at this point was running good again and the bill was on the dealer. Another month and half went by and light came on for o2s, cats, evap leak/sens. And another thing I can't remember. Changed all o2s, both sens on evap can, full tune up with good parts. Cleared light, truck fired up perfect and ran excellent. Test drive.. ran amazing for about 5 miles. Lots of power and very smooth but strong. Bam! It dropped under 2200rpm out of no where. Lost all accelerator, gauges went wiry and lit up. SES and SLIP. Stopped shut off truck for a min. Fired up, lights were even out. Started to drive and it would struggle up to 2500rpm and then take off. Lights came back on and then couldn't go over 2000rpm. "Limped" back to home. Codes now were for accelerator pedal position, TB position, evap sens, and something else I think. Would have to pull codes again. Any who, after a lot of try this and change that and a bunch of money we are at a total loss.. still buying truck even.. And no one has been able to figure it out or even shed light. Not even the Nissan dealer could after 2 weeks of having it.. At this point only thing I haven't tried is a new ecm. And also the lights won't clear, and it won't even take the relearn process for brand new pedal and TB. Yeah.. that's the short.. lol help anyone? Thank you for taking time to read.