Rb25det fuel cut issue. please help

[Subienate95]

I just recently got a new car. its an s13 hatch with an rb25det s2 in it. It was running great when i got it, everything was stock except exhaust, intake, fmic, and it was turned up to 12lbs, and a z32 maf. i took it off the road for 3 weeks to fix some rust, while it was down i switched to synthetic oil, i changed the plugs, put some coilovers and wheels on it. i fired it back up ran down the road, 1st and 2nd gear were flawless, pulled like a raped ape. then i shifted to 3rd and it would die at what my tach says is 6k, which is wrong. tach isnt calibrated yet. it doesnt bog down or missfire or anything it just flat out dies. the wideband says full lean like when your on decel and the injectors are off. i turned it back down to just wastegate spring pressure which makes it boost at like 5. still does it. i cant find any boost leaks. i tried giving it like 15-20% throttle in 3rd to see if it was a boost issue but it still did it. flat out dies at 6k on my tach. i feather the throttle while its slowing down and itll spit and sputter then come alive again and cut out right at 6k again. im at a loss, any info will help. sorry for sounding like a dumbass but idk what changed enough for it to fall on its face like this.