The new cylinder heads started making power down around 3,400 rpm. We expected a slight decrease in boost from our normal 10 psi due to the larger runner volumes, but LaRocca noted that the flat spot in the curve at the top of the rpm range is indicative of belt slippage. We saw 8 psi of boost, but were unable to tighten the belt further as the tensioner has become tweaked a little too much. We'll try again at a later date with a new tensioner and belt to see if we can't get that 2 psi back. Otherwise, we'll just pulley up.