Ran my twin turbo boat today and the engine behaved different in the jetboat vs the dyno. We ran the boat with a50% mix of 110 renegade and 93 oct pump gas. Made 13 lbs of boost at 6800rpm. Correlates closely with dyno sheet/ MPD AA impeller hp estimate of 1300 hp. On the dyno we applied pressure to the top side of the gate to get this number.In the boat we rigged up an AMS-500 boost contoller. Bottom gate port is vented to atmosphere. Top gate is connected to the boost control sysytem, using co2. With the Boost controller off and no pressure applied to the top of the gates,"verified with a Gauge", we had 13lbs of boost..? Lightest spring in Kit. Same thing on the dyno would only make 2 lbs of boost. The difference, other than atmospheric conditions, is we have no dyno exhaust system after the turbo. The dyno exhaust was 5" flex pipe to 8" to 12" pipe with smooth transitions. On the boat the pipes are 2 ft staight with a 30 deg bend at the end. I am a little confused on this. The boat had a 1471 with 2 doms before, much different animal. Testing continues, Plug readins say were very safe so far. Adding 2 deg of timing for next test. was at 28 now 30 total.