Volvo: 1986 760t automatic trans, serveral times, downshifting

Question
I love my 760 to death but there are a few quirks that I think might be leading to more serious problems. Whenever I am decelerating from 3rd or 4th gear and its downshifting into 1st I can hear a loud clang metal on metal sound. It doesn't seem to do it unless I am stopping from 45+ mph.  This has been happening for a year and has never gotten worse and the car shifts beautifully. It only happens just before I stop.  
On a less serious note I can't for the life of me get the car to pass emissions.  I have: run a cleaner through the fuel system, new oil, made sure the car was warmed up, I even noticed my pre-heater hose was not attached properly and corrected that and it still didn't pass.  I have recently been told it might just need a throttle body cleaning. Is there anything else I can do to get it to pass?

Answer
Cole,
That clunk would be something that needs to be felt on a test drive. Have a Volvo tech go for a ride and show him/her the clunk. How about loose suspension or exhaust system, or center carrier bearing?
Since I do not know the reason for the failure, my guess would be a throttle cleaning would not do the trick. Dirty throttles usually cause poor idle or dying out serveral times on a start up mostly cold.