I say AFR 11.5 max and timing 30 total MAX.... I don't care what your doing in a car, the car don't run WOT for 10 minutes at a time....

If your blowing head gaskets there is lean issues.... period....lifting head or otherwise... use cometics and head studs to be safe, not always needed, but not a bad idea...

You can tune on the meth, but that's not smart as if it don't come on your screwed, I run meth in my Cobra on street with blower, but I tune as if its not there, I use it for safe zone...

of course it went faster leaning it out, always will, just not for long.... keep a blower boat engine safe and it will be fine!!!!

I'm sure it blew from extra volume of air over the M1. They were cheap del pro gaskets that were in there. I used cometics and head studs when I threw new afr heads on.

I might have mentioned my timing table being at about 34 degrees at 6000 rpm's at one point but recently reviewing my efi program I see that my spark table is at 35.9 at 5800 at 100 map and my timing boost correction table pulls out 3.9 of that down to 32 when under hard boost, my 6000 rpm number is a touch higher at 36.9 - 3.9 under boost but you better be real sure of your octane quality and have a knock sensor if your going to push it right to the edge like that so I would NOT run that much timing if you just went from 110 psi of cyl press to 145 and added a bunch of boost just to be safe.
As far as your current problem, the obvious thing to do would be to try a 26 labbed prop and see what that yields, a dyno session would be next if its still slow and doesn't rpm and you cannot find anything else. I did not dyno my motor the last time I freshened it and I am regretting it now as I am missing some rpm's and speed on very top and it is very hard to get perfect and safe conditions to do testing/tuning to figure it out and I have wasted a lot of time chasing this crap. I will NEVER skip the dyno again as it is so much easier to see where you are at and solve these problems without having to buzz up and down the river at 100 mph while trying to find a problem without killing yourself or breaking stuff, Smitty

Sounds to me like all you upgrades are making the motor detonate and your loosing performance... You were ok leaning it out a bit but as soon as you put some compression in the motor you lost performance. An easy way to tell would be to slow down the blower and see if you pick up some performance.