I have two questions:

[1] What do you do for power steering fluid? Do you ever flush and replace? If so, would you reccommend using a synthetic fluid.

[2] Do you reccomend any additives for the fuel injection system?

I have a 2005 Grand Caravan with just under 50,000 miles that I would like to keep in good shape.

 

A blanket answer is to keep ALL the fluids clean for the longest life.
You can use a rare earth magnet,securely supported by a wire,left hanging in the power steering reservoir to collect ferrous metal particles from the fluid.

I don't like fuel additives.They don't work very well at the dillution levels recomended.Every time you shut the engine down a little bit of fuel dries on the injector tip and on the back of the intake valves.This will build up over time if the runninginterval isn't enough to clean the old deposit off before a new one is left behind.A drive of thirty minutes to an hour can be required to clean off even light deposits.
Cleaning the internal parts of the engine is best done by driving the deposits away.This can take a long time however.I prefer to use a spray type carb cleaner introduced at a point before the idle control solenoid.This cleans pretty much everything downstream of the spray nozzle.A couple of cans might be required to get everything truly clean.This won't clean the injectors internally very well though.Solid particles will need dissassembly to completely clean them out and varnish deposits can be cleaned with additives eventually.Lots of short drives will still cause the build up of evaporated fuel and the additives can make the problem worse.

 

In response to your questions. 1. Most of the time flushing power steering systems is not needed or recommended. However, if you do require a flush due to a problem I always use synthetic fluids. 2. The fuel system needs periodic maintenance and you are due at your mileage. I suggest taking it to a dealer that can give you a fuel injection service. NOT A FUEL INDUCTION SERVICE. The difference is the fuel injection service runs cleaner directly into the fuel rail and cleans the fuel injectors as well as the intakevalves. Fuel induction only cleans the valves andruns cleaner thru the throttle body only. The fuel injection service usually runs about $100 and is a 3 part cleaning solution. Part 1 is run via the fuel rail. Part 2 isadded into the throttle body to cleanintake runners and valves. Part 3 is added to the fuel tank and cleans asyou drive.

You should also consider using the tankcleaning solution on a regular basis and have the fuel injection service done every 30 to 50K. You can tell the difference in theperformance almost immediately.