Recently I have noticed that when iam driving my RX and I go under boost I notice some shuttering. I was thinking maybe the cars running lean from a old fuel filter ( I just bought the car) and making the engine bog either that or the spark plugs are going bad (no clue when those were changed either). Anybody got any ideas?

 

I'd recommend changing those no matter what when just getting an FD. At least that way you'll know where you stand with the car's maintenance:

* Change fuel filter
* Change air filters
* Change oil and oil filter
* Flush coolant
* Change plugs (check plug wires to see if they are still ok)
* Check and clean grounding points

That will at least give you a good place to start.