I have a 406 in my 78 Jimmy with Edlbrock alumiun heads & intake. I had a intake leak on #6 cyl. so I changed gaskets.I found the gaskets on both sides to be distorted, as in curved toward the middle of the port.Between 6&8 the middle was gone, & the top sunk in causing an air leak.These were Fel-Pro gaskets been on for one year. Anyone else heard of this? And no the intake was not lose.