my left rear caliper is slowwww to release, also when attempting to bleed almost no fluid wants to come out, I though maybe a collapsed line but could it be the caliper itself, btw. rear calipers are 914-4 front calipers...911 M's in front.

There are not that many moving parts in a calliper and fluid moves the piston. If you take it apart, first get a rebuild kit and might as well do both, you will most likely see some corrosion on the side of the piston whic impedes it's movement unless the tolerence is huge. Happened to me once on a bike front calliper which squeeled like a stuck pig.

collapsed line is most likely

How old are the flex lines? If they are old they can internally swell and act like a check valve.