I'm leaning toward the I/C pump. My SRT was doing the same thing and I "thought" the transmission was slipping because of how it felt. One time, the car would lay you back in the seat and 2 minutes later it would be doing nothing even though the RPMs were way up. That's what losing 115 HP in an instant will make your brain believe. I doubt that any shop will pick up on this - I came here to find the answer.

If you decide it's the I/C pump, several people have replaced their OEM pumps with a Johnson CM30 but you will have to modify the mounting bracket and the electrical connector. Here is the latest Bosch pump that will replace the faulty OEM with no modifications required.

http://www.amazon.com/Bosch-0392022010-Engine-Auxiliary-Water/dp/B0071N4Z0K

Good luck

RL