Lo side 7 hi side 225 compressor replacement was 502 now 404a , cro valve replaced,drier replaced system flushed with rx11. System appears to be operating good brings unit down to -15 . amp draw 7.2 restarts great cro valve working. my problem is suction pressure seems to low. I weighed in charge 90 percent of name plate of 30 ounces.

SOURCE: What is the normal operational

why yes there is. Generally speaking, the head pressure should be around the "ambient +30" rule.
That is, measure the entering air temp to the condenser, say 75 degrees. Now add 30 to that and get 105 degrees. Look at a P/T chart and see what the pressure is for that temp which is about 253 for R-404-A.
The evap on a freezer leads the load so, as a general rule, the evap temp is going to be around minus 10 degrees to get a 0 degree box. Coolers are different. So, the pressure for a minus 10 evap is around 25 or so. But the unit has to be close to operating temp. If the box is warm, naturally the pressure is higher. And what influences the pressure is whether or not it's a TXV or a cap tube system.
If a TXV and no receiver, charge by subcooling. If a receiver, fill by sight glass. If Cap tube, charge by superheat.
Hope that answers your question.