Negative G causes FPS to rise substantialy

[palker4]

Today i was flying quick mission Bomber intercept Hawkinge and i have noticed a strange phenomenon that when i push my stick to neg G so that my engine start loosing rpm my FPS will increase from around 25 to 60 and i was wondering how is this even possible.
There were 8 Ju-87s and 6 Hurris in that mission. I used fraps benchmarking tool to create FPS graph. Take a look every single spike on that graph is cause by me pushing stick forward.