I was thinking the one inside the older style controller.
The one on the pressure line.. good luck.
Anything that sits in methanol or alcohol needs to be brass or stainless.. Long time ago Autometer made an inexpensive fuel pressure gauge using an oil pressure sending unit.. the alcohol in the gasoline would cause them to fail eventually leaking.. there was a recall on these gauges because of that.
Sorry cant help further, you may try and see if Steve at SMC still answers his email.. Should be in your paperwork if you bought the kit from him.