Review on Autolite AR3910 4PK Performance Racing Non Resistor by Matt Jenkins

Used these in my VW 2.0 at max timing and high octane but still needed some cooler. I called Autolite 855.200.5200 and spoke to Marty. He told me that the AR3910 would be colder, in order would be AR3932 and AR3931. 31 is the coldest connector they make in this configuration - thread size, key size etc. AR3933 has the same heat range as 3910 but without the extended tip that 3911 and 3910 have. In that sense, 3911 is hotter than 3910. 33, 32, and 31 have a standard tip, not extended. Marty sounds like he's been there since day one. He has knowledge and answers and was happy to take my call. Hope that helps.