I know what you mean, I have also tested a few engines and in off-road races most of the time you can't tell the difference in engine power when all of them are very close to all...power/design/quality...especially the last 2 years.
There are of course the exceptions to this...my two hyper 4 ports...changed the sleeve from one to the other and guess what, it's exhaust port seemed 1mm higher than my previous sleeve when looked from the exhaust on the block.
I don't run off road anymore I turned into rally game on-road 1/8th races and you can really tell the difference between engines especially out of a 180 degree slow turn. You can see the difference of the v-spec down low compared to all the other.