2003 engine stutters and or stalls

hello everyone. I just bought an 03 windstar 2 wks ago. bought without speedo odo etc. working, fixed by master cylinder switch. also changed alternater and cel codes 171,174 are on. Engine seemed fine for 1st wk, it has 200k km on it. At hwy. speeds, motor stutters or chugs for 1 sec sometimes, tach drops, then gets better. engine feels sluggish now also, and now it has stalled on me numerous times at different speeds. It starts right up again. AS codes 171,174 are up, I will look for and get vacuum leaks checked, fuel pressure checked /filter changed, pcv tube and valve changed. some one wrote could be the maf sensor or tsb 3-16-1 problem. Has anyone had any similar experiences?, Any help or ideas would be much appreciated. I hope I didn't just buy a lemon.

I'd start with cleaning the EGR ports and replacing the intake plenum gaskets. That's usually what causes the 171/174.

http://leckemby.net/windstar/windstar01.html