Reg Z defines a HPML as:
“Higher-priced mortgage loan” means a closed-end consumer credit transaction secured by the consumer’s principal dwelling with an annual percentage rate that exceeds the average prime offer rate for a comparable transaction as of the date the interest rate is set:
My question is if a mobile home(principal dwelling) that is located in a park,the owners of the home do not own the land and we secure interest in the home through a UCC filing would this still be considered a HMPL if it exceeds the APOR?

Yes, mobile homes (with or without land) are included in the definition of a dwelling under Sec. 35. From 1026.2:

(19) Dwelling means a residential structure that contains one to four units, whether or not that structure is attached to real property. The term includes an individual condominium unit, cooperative unit, mobile home, and trailer, if it is used as a residence.

Thanks