[86TOYO2k17]

Recently I noticed my car was bogging down and bucking at low throttle, low rpm so I started looking st my fuel trims and at idle, low rpm, low throttle my STFT and LTFT where both around negative 15% (30%), at Highway cruising as well as WOT they are both around 0. I reflashed my tune and car drives better but LTFT is slowly creeping back up as well as STFT being around 15%.

Another issue possibly causing this just never noticed fuel trims from lack of driving and lots of reflashes. I had a shop put on Crawford billet Blocks and a ace 250 header/op. At the time everything else was stock. Besides OFT tune. But only in gear and I only hear it in 1st-3rd gear at exactly 2500rpm and 3000rpm there is a high pitch sort of whistle sound, like a hybrid between a kazoo and a whistle. I went back and had him do a smoke test and he said he didn’t find anything, although idk if I trust him...

From my understanding a high negative fuel trim is from too much fuel. Could this sound have something to do with fuel injector and or fuel rails? Or is it possible exhaust leak at header or OP or vacuum leak at manifold or a loose hose could cause this noise as well as really high negative fuel trims? What should I do?