see problem with L92s is there thin decking. a stock head is about .5 thickness the L92s are about .45 thick. now what makes the AFRs a great head for boost is they have a .75 thick decking. these allows for better sealing of heads when comes to higher boost levels. they say up to 15lbs heads seal fine without any question. now anything above that its questionable if they will lift or not.

now even rick from syenrgy even spoke on how he doesnt like the L92s for boost and the 317s are much better for performance.

Parish made his 1011rwhp 1070rwtq with stock 317s on his 408.