Q: hi, what can i change on my 2006 4runner to give it smoother ride on bumpy roads

There can be some gains in comfort by changing the tires to, for example, top rated tires as tested by Consumer Reports. The best thing to do is review Consumer Reports’ tire ratings and recommendations for the particular tire type and size that you use on your vehicle. Tires do make a difference in terms of noise, tendency to vibrate (due to radial force variation), absorption of bumps, and so forth. As an example, Michelin tires are often notably quieter than other brands and better made, too. But there are other good tire manufacturers out there these days as well. So, you might see some improvement based on changing the tires. As far as the suspension is concerned, the safest practice by far in ensuring optimal ride quality is to use OEM dealer supplied shocks and struts. As you can imagine, Toyota has an army of engineers and highly trained technicians who have already agonized over how to maximize ride quality on each vehicle model they produce. If you did not use OEM shocks reverting to that will probably help as well. There are not any "practical" aftermarket solutions though partly because you would be in effect re-designing the vehicle suspension or doing ad hoc experiments with various equipment modifications and that is not only not practical but is very costly. If you desire that the suspension be inspected to see if there any overlooked deficiencies, worn parts or the like, the recommended service is a suspension inspection.