I can't edit a topic title, so this is just to point people at this thread, which is relevant to Fantastic Journey as well:
http://www.gog.com/en/forum/pro_pinball_series/big_race_usa_performance_suggestions

FJ has severe lag between when you press the keys and when the flipper flips.
But the graphics don't lag.
Is there anything I can do to fix this?

You don't say whether you followed any of the suggestions that I linked to (and which ones you tried, if you did). If you're unfamiliar with something I've mentioned, let me know -- if it's easy to explain, I'll happily do so.

I did the same thing as you mentionned in your other topic and it fixed the graphics slowdown.
But it just doesn't respond sometimes.

The other thread mentions all of the following:
1. motion blur settings
2. windows compatibility mode
3. processor affinity
4. audio hardware acceleration
Which is why I worded my last reply in the way I did: