From what I have seen, this engine is very sensitive to heat. I have seen 1/4 mile results of these cars constantly running 2-3 mph faster at 56-57 degrees compared to mid-high 70's. 2 or 3 mph of trap speed is about 20-30 hp. So, what you are reporting sounds about normal to me. This is also something I have noticed when driving my car at different temperatures. It just seems sensitive.
I'd recommend putting it on the dyno again with similar temps/cool down times. That is the only way to get an accurate comparison.