Hi -- I recently bought an 07 Tahoe, 87K miles, original shocks. I pull a 4K lb trailer for work and the ride is a bit bouncy. I previously had a n 05 Tahoe w/ the air suspension and had no bounce problem. Do you think changing the shocks to more heavy duty ones will resolve the bounce, or do you think I should change the springs, or both? And if shocks, Bilstein? Are there different models of Bilstein? If so, which one should I get? Thanks!