I can only attest to what my experience was with MTC. I went through 3 MTC monovalve kits last year (1 in May, and 2 in November). They all failed the same way in that they had little tiny holes in the rubber diaphragm. This caused no heat at highway speeds. I installed an OEM in November, and it has worked flawlessly. I was paying about $30 for the MTC kits, and the OEM was about $120.

As an aside, I also installed an MTC aux pump at the same time. It lasted 1000 miles before the screws holding the motor to the pump housing loosened causing me to lose most of my coolant in downtown Chicago. It sprayed all over the engine compartment, and I was not a happy camper. I tried tightening them, but they just kept on loosening. Installed an OEM aux pump, and it has worked flawlessly.

No MTC or URO parts for me. EVER.

Jon

1985 300D 107k
1968 250S