Any AC Techs

I wouldn't give it a second thought 134 runs higher pressure than R12. also, it does not have the good cooling qualities at idle in some instances as R12. I would simply charge it with the recommended amount and call it a day. Not uncommon for high side pressure to exceed 300 when it's hot out. i still do A/C work for friends, church members and family as Im still A/C certified.....not that that means much, but I've done a lot of A/C work and your situation sounds pretty normal to me. As stated previously, if you do not have a cycling switch, you certainly need one.