MagnaFlow exhaust revolves around the idea of increased flow through the system so things like baffles, chambers, louvers, and flapper valves are eliminated. This allows the system to achieve its tone as well.
I know a lot of people like to disable the displacement on demand or active fuel management systems that cut the motor to 4 cylinders when it chooses it is appropriate. If this is something you are interested in then the way to achieve it is to use a programmer that will allow you... view full answer...
In terms of cost, the MagnaFlow systems are 100 percent stainless steel. High grade stainless steel cost more than lesser quality stainless steel used in systems like those you can get in auto parts stores. I had one of these systems installed on my 2006 Pontiac Grand Prix GXP and it was awesome. Plus the systems have a lifetime warranty, they are not going to rust out like factory systems would, and in my case they brought up the vehicle value a little. The slight boost in power and fuel... view full answer...
The Coil-Rite helper springs # F4155 fit inside of the rear coil springs on your 2013 Toyota Sienna. The exhaust is not close enough to cause any problems. Also, the coil springs themselves would also help dissipate any heat. I have included a link to a video showing an example installation for you.
Like you said, the Air Lift springs # AL60732 do come with a heat shield as a fail safe. I have linked a video of this kit as well. The Air Lift system is a good value so if the heat shield... view full answer...