Rolling anti-lag and bent valves

I have an issue that I need some expert advice.

I have a USDM Subaru Legacy with a EZ30 H6 swap that I turbocharged and wired in a Haltech Elite 2500 to run it. It has forged pistons, rods, closed deck, Supertech valve springs and retainers, and 12mm head studs.

The issue is it keeps bending valves when I use the rolling launch. The odd thing is that I used the rolling and stationary launch many times (over a year) with fuel cut and -5 degrees of timing and didn't have any issues until recently. It bent the exhaust valves in cylinder 4 about a month ago for the first time. I got it fixed by throwing on a used set of heads and then added some timing into the timing compensation thinking it may have been too aggressive and popped the valves open.

I just went out and tested it again and it bent the exhaust valves in cylinder 4 again! This time the rolling launch had the timing compensation at 5 degrees. It was noticeably less aggressive.

Is this something anybody has ever seen with launch control? I find it odd that it worked fine for so long and now I'm having issues with the same cylinder with different sets of heads. Anything mechanical I can look at? Or is this engine just anti anti-lag? I uploaded a pic that shows where the piston hit the valves.

I'm 99% sure the root cause is the valve springs - especially if they weren't installed to the correct height and/or weren't the correct spring rate and length in the first place.

The problem, I believe, it there is sufficient pressure in the exhaust manifolds to prevent the exhaust valves closing properly, or even actually opening them, against the spring force. The running engine will load the engine differently from fre-revin'ing, and so may have different pressures developing in the manifolds and cylinder. Depending on the manifolds' designs and the turbo-charger location, it's also certainly possible for one cylinder's exhaust port to see more pressure than the others which is why it may only seem to be happening on one - have a careful look at all the rest, though, as some may be making very light contact.

The easiest fix would probably be to change the valve springs to stronger ones - Supertech have three different spring sets listed for that engine, with different seat heights and seat pressures, you need to check what you actually have and how they're installed, then make the changes you need to make. This may even be a different brand.

I would also suggest reviewing the manifolds.

Awesome, thank you. It probably doesn't help that the valve springs are the same ones I used when I first built this setup 3 years ago. Maybe they've gotten weak. That would explain why I had no issues for so long, but am now having problems. I'll look into valve spring options and get a new set when I have the valves replaced.

The other thing which is probably more relevant is are you running shim-less buckets? If you run ALS with aggressive spark cut you get explosions in the manifold which cause big pressure spikes and lift valves; this can spit shims out. I've used under bucket shims in my v5 STi Type R rally car for years with no issue but I use fuel cut not spark cut.

The exhaust valves have shimless buckets on this engine.