How do I know if I need a Slave Master Cylinder??
 

My car when you drive like you have since you can go through the gears fine. If you drive it hard and the revs are up the clutch goes to mush and it refuses to shift into 3rd and 4th. I have already bought the new Slave and ordered the Clutch today. My question is when they updated to the new style did they change the Master Cylinder at all and should I look into getting one? The car is a 98 SS and from the best I can gather it has less than 30k miles on it. I plan to do the drill mod and before I go and spend 160 for a new one I wanted to make sure I wasn't just throwing parts at it.

I wouldn't worry too much about the master. If the new slave and clutch don't solve your problems, you can change the MC later. I don't think the master was changed but I could be wrong...

It's probably a good idea to do the drill mod. I only did the drill mod after I got an updated 01-02 master. The stock 98 master had a different push ring for the hydraulic line. The old one has no lip, it's simply plastic that wraps around the quick disconnect and requires the screwdrivers to be dead on. The new plastic on the updated master has a lip on it that makes it really easy to get a screwdriver on it, actually last time I unplugged it, I just used my thumbs and pressed with my nails.

The drill mod usually solves the mushy feel of the 3-4 shift and sometimes the 2-3 shift.

I changed my master in my garage with no probs. Also note that once disconnected from the slave, the master shouldn't budge. If you depress it a good amount, the seals may be going or it's leaking.