I had the same problem on my 1999 Supra Santera. The high pressure fuel pump is water cooled. There was a recall on it. It was supposed to be bypassed. Yours, like mine, must not have been done. Now you have a pin sized hole in your high pressure fuel pump, causing gas to leak into the exhaust. You have to replace the high pressure fuel pump, and bypass the water cooling canister. Good luck if you haven't already figured it out.