Is there any chance your over-tightening the carb manifold adapter bolts? I have seen this done more than once. They don't need to be super tight, just snug-em up and forget them.

The G10 DA manifold adapter will work with a little effort.

I'd suggest tightening the four cylinder retaining bolts. After a run or two its a good practice on a new engine and or installation to check all the engine and mounting bolts to make sure things have settled down and heat seasoned. Don't forget hte prop bolts and especially the muffler/header bolts.