VERIFIED SOLUTION i

How to know why MailStream Plus gives a mail piece a Full Service, Basic, or Non-Auto Service Type ID (STID) in the Intelligent Mail Barcode (IMb)

A Mail Piece will get the Full Service STID if it is eligible, and the job is asking for it.  For example for a USPS Marketing Mail letter, it must be:
1) physically Automation Compatible, 
2) have a full ZIP/+4/DPC (Delivery Point Code), 
3) the ALG PP parameter must be set to F or Y in position 10 to tell MailStream Plus (MSP) to attempt Full Service.
See chart below.

What STID values are used in a job depends on what services the mailer wants from the USPS.  
In the examples below 702 is the STID being used for Non-automation in IMBOUT position 32-34.
For the Full Service IMb Mailing, 037 is being used in 36-38.  Currently the USPS uses the same STID value for Non-Automation and Basic STIDs, so for the Basic IMb mailing 702 is also being used in 36-38.
The chart shows which pieces got 037 Full Service, and which got 702 (Basic or Non-Auto)

Physically                           Full Service job                Basic job
Auto or nonauto                  With Y or F in ALG PP pos 10   With N or B in ALG PP pos 10
Compatible?                      (IMBOUT 32-34=702 36-38=037)   (IMBOUT 32-34=702 and 36-38=702)

Auto             has full ZIP/+4/DPC      037                         702
Auto             no +4/DPC                702                         702
nonauto          has full ZIP/+4/DPC      702                         702
nonauto          no +4/DPC                702                         702

So the only pieces that would get the Full Service STID of 037 were physically Automation compatible, with Full ZIP/+4/DPCs, and the job was set to Full service in ALG PP position 10.
UPDATED:  August 4, 2017