Is R407c compatible with R134a

ok stay at2lbs low side

no absolutely not! Those kits are also more trouble than they are worth if anything at all is not right in the setup. Its worth going and having it done proper, and its not too pricey as long as you phone around enough.My shop in NB charges $10 per pound and a flat rate for labor depending on vehicle. You will burn out the AC in about a month on the wrong refrigerant, they have r34 in r407 as straight up r407 is no longer legal as pure.