Hi, Have you tried using half halts? if you havent gently pull your outside rein to slow him down, it works for my rushing horse. Hope this helps

Sounds like he loves jumping, and is used to jumps meaning 'go fast!'. The other suggestions are all good, lots of schooling, flatwork, school with jumps in the arena but don't do them. Try and reprogram him so that jumps are optional and he only does them if you say so. I'd avoid a stronger bit or gadgets, simple schooling will eventually get him out of this. Make sure you sit tall, calm, look forwards to where you want to go and think positively. Maybe you could have a jump lesson on a different horse to see if you are signalling him subconsciously. You may get a little tense when jumping as you know what he's going to do, and he feels this and gets het-up. You say grids work, what happens for him to rush again? I think he may have to engage his brain more when you introduce a grid, so he slows, thinks and is sensible. Then, after a few goes, he figures it out and feels confident to rush like normal. Try changing what you're doing before he reaches this stage, so he is always thinking and listening to you. Spreads, different grids, small courses. Do interesting things like put up a small cross pole, hop over it, circle, leg-yeild, do a couple of transitions, go back to the jump in trot, hop over again, stop, rein-back, etc., etc., so he never knows what he's about to be asked. If he throws his head, he's probably resiting the contact, at which point I'd say turn him instead of trying to stop him, and circle til he's calmer then try again. Use your seat as well as your hands and try and avoid fights!