You want to look at static FP (with regulator vac line off). With a stock 233 regulator static FP should be 34-40. With the 237 regulator (what came on the TTA, and is considered an upgrade) static FP should be 37-43.
With the vac line on the #s will go down roughly 6+/- psi. Focus on the static reading, and then when your driving watch that your FP rises with boost (FP should = static FP + boost).
If you have a custom chip and an adjustable regulator, then set the static FP at whatever is recommended by the chip maker, and start there. 43~psi static is usually a good # to start with.
