I have a Winstar 1995. 3.8 with 171/174 codes I´ve heard that the TSB 03-16-1 it´s only for 1998 and older. Where can I star to check? Thanks from Guadalajara, Mexico. Adrian Zapata

As far as I know the TSB you refer to is for 99 and later models.
There is a ton of help on this site in previous posts from fellow sufferers like myself. Basically I'd recommend that you start by checking for any vacuum leaks you can find and take it from there.
It is a process rather than a quick fix.