Enginetech valves

They are stock builders parts.
Meant to meet OEM and or a hair better.
They are not a performance valve, just like a stock valve in a 1971 340 x head isn't a performance valve either.

They make some upgrade stuff and their gaskets are as good any other in their intended usage. For instance I use Fel-Pro stock replacement PT8553 with 10.1 and cranking over 180psi. Head gaskets have never been an issue. They work great.
Probably at their limit, then again a bad tune can ruin anything.
Not to Veer off but I remember an article where Mopar Muscle or Car Craft or whichever rag printed that same build popped some of these gaskets on the dyno with a 10.1 motor but I highly doubt that it that even cranked that much...I think they're just idiots that couldn't even get a tune with a fkn A/F monitor, on a Dyno even.
Nutshell they're great, just dont use them with solid roller pressures and they won't snap and destroy everything.