No their is not a special tool if i remember right to get the exaust off. The hissing is not normal.

As for the thumping i would have to be their to actually tell you a right answer. Could be the plug wires. i think my rx7 did the same thing later i looked into it and it was arking. idk if it could be the oil tho. Jus what i think may not be right but id go over the ignition system