Maybe you are trying to trim too high to get RPMs, and that is what's making it too loose and flighty. Maybe a prop change is in order.

Have you driven v-hulls.... No steps...? Gotta hang it out to get speed. It's a learning curve. (I have never driven one of these boats.. But I have driven a bunch of fast v-hulls.) start by over trimming at lower speeds and playing around.... edging the wheel inputs to the left.

But who knows...

its got a stock bravo 1 28p on it from what i can tell, doesn't look to be worked over at all.

the tremor has a step in it, not a very big one tho, maybe a inch, inch and a half. driven lots of straight v hulls and had been use to feeling it ' break free' as you trim up this one never has that feeling like your ' popping it' out of the water. i played with trim and lower speeds and found its porpoise point and make sure to not cross it at speed, i would set the trim at cruises speed, about 50mph to get the most speed with the least rpms, its usually just a hair off full down, maybe the gauge needle thickness up, not much more or i start to loose speed and gain rpm, have tried as high as trimmed up to the 3/4 mark - first line on the gauge up from full down - also right near the porpoise point and it will run hard but starts to walk. it does have full hyd steering with the merc ITS

Does it have a stock length drive too? How far below the keel is the propshaft centerline? The drive may be in a little too deep for that setup which causes you to trim it way out and get loose versus a shorty lower requires less trim to free up the prop. From what I've gathered, with few exceptions, almost every single engine vee bottom over 80mph is going to take some learning, testing, and eventually you may just reach the hulls limit. If it has full length strakes all the way back, that may be too much lift at 80+mph, but it provides a lot of lift for a 496 boat. I'm in the same boat, mine starts to chinewalk over 85.

it looks like a standard length lower with the its, witch as i think i understand is the same as running it about a inch deeper then having it mounted right off the transom? i haven't checked how deep it is yet, been to busy driving it haha, but that is my next thing. i was able to get a couple fairly stable passes in the 80-82 area with a glass lake and counter steering the chine, im going to replace all the bushings on the steering arm mounts and change up the colum, it has some play in the tilt and thinking it may cause some free play in the steering at speed.