at the very least, you need to verify if there is a screen before the condenser (front) coil, and see if any debris are present in it. if not, you will have to disconnect the suction line from the evaporator, and the compressor, and fill with flushing agent, and blow it out and look for grit or slime. next you will have to remove the lines off the condenser. the 99 will have a parallel flow condenser, so if debris are present in there, it's impossible to get them out. there better be a screen upstream of it. then the lines between the condenser and the dryer will need to be flushed like the suction was, and the dryer replaced. then the line between the dryer and the txv also flushed and the txv replaced. then all seals replaced, and reassembled, then leak tested, then evacuated and recharged.
not easy, or cheap.

__________________
John HAUL AWAY, OR CRUSHED CARS!!! HELP ME keep the cars out of the crusher! A/C Thread
"as I ride with my a/c on... I have fond memories of sweaty oily saturdays and spewing R12 into the air. THANKS for all you do!

My drivers:
1987 190D 2.5Turbo
1987 560SL convertible
1987 190D 2.5-5SPEED!!!

1987 300TD
2005 Dodge Sprinter 2500 158"WB
1994GMC 2500 6.5Turbo truck... I had to put the ladder somewhere!