I had the same issues 15 years ago (thought they were made in Australia??) with their manifolds for a Chrysler. Flanges didn't line up, Because of runner tube being wrong I had to dent in a couple runners to get the bolts in, after a year the "water box" around the tubes cracked and started to leak. They were under warranty but required the manifolds to be sent back (to Australia) for a cost of $350 bucks and took 4 months to get back. When they were away I dumped the Chrysler and went BBC and sold the manifolds as soon as they hit my door. I would never buy Hi Tec even though like you said it should be a good design.
A winner is just a loser that got up and did it one more time.
1959 Biesemeyer - 4pt Hydro Drag - 2013 ACBS Winner - Best Race Boat
1967 Nova Marine - SuperNova24 - ACBS Winner - 2012 Best Race Boat - 2016 Peoples Choice & Best Non Wood
1972 John Allmand - Nova 19
1972 John Allmand - Nova19 (#2)
1982 PolarKraft -Jonboat - Crab Killer