Slipping the clutch is a bit easier to explain how to do correctly than I have seen so far in this thread. Hard to do, easy to explain.
Each car should be launched at a high enough RPM to put the engine in its power band immediately after the launch. We are lucky, we are V8s w/ good torque early on so we don't need to launch at +4K RPM or anything crazy.
Next time you are at the track:
Pick an RPM to try
While you launch, don't let the RPM change
Try to get to complete release of the clutch as fast as possible w/o wheel spin
As everyone has mentioned, vary the amount of throttle and clutch pressure to get this done. It eats up the clutch, but it is a much faster method of launching if you are willing to go up to as high as 3K RPM. How high you can go is really only limited by how rough you are willing to be on your clutch. However, lack of traction can make effectively launching at high RPM very hard on the clutch, which is why we don't just look at our dyno's for our cars and pick a launch RPM that is nicely into the powerband. There is a compromise, if the track is not well prepped and has poor traction, then a compromise is in order.
When I still ran 245s in the back my best RPMs for launch were 2400, but there was almost no track prep. Now, w/ 315s, it is more like 2700 RPM.
2000 is a rather a bit low to be maximally helpful, IMO. Practice keeping the tach at your chosen RPM during the whole launch phase and when your pretty good at that it'll be helpful for you to experiment w/ different launch RPMs and see how they work out for ya.
BTW: I got better 60' times in my car with ~22psi than with >30PSI and I use Nitto 555 street tires (not the DRs) as well.
Also, the weather's affect is best shown in your speed at the end of the course. If you didn't miss shifts, bog badly at the start, etc - you can get a good read on conditions based on your trap speed at the end of the run.
At 98.3 MPH, that was not a good day. lol Part of a bad trap speed could be not launching at a high enough RPM to put the engine in its power band immediately after completing your launch. So that could be part of your 98.3, as well.
I didn't have gears, and had nothing but a
K&N filter, but I got my car into the 13's when I still had 245 tires in back (see sig). However, that was at my track, and as the >100MPH trap time in my sig shows, the conditions were rather good that day.
A few months ago, I went out to the track and had trap speeds around 101.5 MPH. I got to 14.0X before the weather even had a chance to really cool down that day. However I was out of practice launching, so my 60' on the 14.03 second run was horrible at 2.25 seconds. Then I had to leave early and never got the chance to do better. Too bad, 13's were in the air for later that night if my schedule would have let me stick around.
Have fun, you will find a day w/ good conditions (and so >100 MPH trap speeds) and will get into the 13s if you've practiced enough by then.