Usually new models mean new EPA modifications as well
I went to buy an HL90 and the new model was the only one available. I bought the HL100 instead since they had the old style that would parts interchange better with rest of my 100 FS90s, FC90s, and HL90s.
The new model was he HL91. Just glancing at it I saw it had different plastic, different trigger/handle, different gearbox, and different carb. I'm probably going to have to start buying 90, 100, and 110 power head equipment off CL for awhile so I can delay completely overhauling my parts inventory that has been so painstakingly streamlined over the last 4 years.
Every time companies do this my loyalty slips a little. I get it progress and all that....sometimes I think they only do it so they don't have to lay off a bunch designers.