1. Never mod your car. If you think you have problems with it now, you're going to flip your s*** with all the new ones the aftermarket will bring to it.
2. I hope your putting all your work orders in a folder and keeping it somewhere safe. If they say theres nothing wrong and you point out that you've been bitching about it to them since day one when it finally fails, you'll have a lot more leverage.
3. You had a Delta 88? That was an automatic correct? Not saying your a bad driver, but have you had someone that always drives stick drive with ya to see if you were doing anything wierd/wrong? I've got a friend that goes through clutches like nobodies business when I never do, and I drive 10X more aggressively - we both have a focus and a mustang gt. Your driving/shifting style could have a lot to do with it too. If you can police someone up and just have them watch you drive to see if your doing something different, maybe they can help point that out to you.