I have the twin 150 HPDI's on my HS and love it. No issues and ran it since new in 2003. I agree on the Fitch HS - many older ones out there and I did not conside the HS until I could do the Yamaha thing. I have not yet ridden on the F150's but from what I hear a little slower out of the hole but when you figure total cost & maintenance of both types of motors they are about equal. V6 vs V4 but again I have not ridden in the F150. I think you will be pleased with the HPDI's the smaller ones have not had the issues of the big boys 250 & 300.