You need to give us more info about the 'bouncing'.
It could be kicking up because it's too hard - unlikely with the set-up you have.
Or...
It could be hitting the floor and bouncing back up because of that - more likely with your set-up imho.
You can check the above by getting a friend to watch it closely along a section of track and also put some tape on the back of the chassis as an indicator to it hitting the floor.
Did you say it feels 'really stiff'?
It shouldn't do with the set-up you've posted, is it built right? Do the wishbones drop under their own weight?
Perhaps that is the problem. Make sure NOTHING binds at all in the suspension without the shocks fitted.
G