I replaced my canister a while back. Purchased it from Amazon for $70, Motorcraft CX-741. I don't know that it needed to be changed, but it wasn't all that expensive and looked pretty dirty overall, when viewed in the intake ports. As many have mentioned, the new canister does not come with the intake caps, but they transfer easily.

 

Many Thanks for all the information you posted Al!!!
I've copied your postings and fixed my '97 3.0L. Just got back after resetting the error and a long road test. Everything Torque Pro and My Car apps can read passed so I'm ready for my semi-annual emissions tests to renew my plates. I'd replaced the hoses thinking they were the problem but the light came back on. I washed out the purge valve and flow sensor with Mass Air Flow Sensor cleaner and that seems to have solved my problem. Just to be safe, I think I'll order another flow sensor because the readings I got seemed pretty low. I'll print this out and stick it in with my factory service books.

 

I'm glad you were able to use my notes. I sold my last Aero last year, replaced it with a 2010 Sienna AWD, which ain't no Aerostar!