Sudden LQ4 problem??

[2014sierraAT]

Ok guys I’ve got a gen 3 lq4 out of an 05 Silverado with the 4l80 it started life with. The motor/trans is in my 70 c10. When I first bought the truck I had it serviced, and had it tuned by a reputable guy we have here locally. I put probably 3500 miles on the truck in the first 6 months I had it with ZERO issues whatsoever. Recently I put a k&n cold air intake/filter on the truck, (engine is bone stock by the way). Some time after the k&n swap I started noticing big dips in the rpm, (at idle) which was causing my oil psi to fluctuate also that worried me. Now it’s not only fluctuating 500+ rpms at idle it’s also doing it at highway speeds, and causing trans to shift really hard. I spent about 1.5 hours driving the truck yesterday with the tuning guy, he adjusted tables that were altered when I put the cold air intake in on. But the truck didn’t have one issue like I’ve mentioned while he was with me on his computer. Any ideas??