always worth while getting it checked out. What you have to remember is that you have gone from an 8v which i have always found to have better low torque, to a 16v which is better at revving through the range.

As for the filter, stick with what you have. Can;t really get much better than a pipercross. Don't really know enough about the power boost valve. Believe they up the fuel pressure. Maybe worth while if you were going to chip to ensure that you have the right amount of fuel required so as not to run lean.