Rev flare issue

First time poster and new to tuning so please go easy on me 🙏🏼

I converted my range rover classic to LS1 (long story short I got massively stitched up on the "full conversion" I purchased)

I am running a 3" snorkel into a universal airbox
Exhaust system is 2½" into 3" no cat but a large muffler and small resonator.
I have no vss sensor and the standard Landrover r380 manual gearbox.
I am running 2 02 sensors up the front and no rear.
Speed density.

I have an intermittent issue with a rev flare
Sometimes when I start it, it'll rev to around 2200rpms then drop down after a few seconds (sometimes it'll stay revved up)
Occasionally it'll also hold revs for 5 seconds while driving (noticeable when changing gears or decel)
Sometimes it's perfect and doesn't do it at all 😅

I have attached a drive log (I think) that shows the flare when changing gears.
If anyone could help that'd be amazing!