904 tranny problems

It started backfiring while idling after warmup. The engine and trans sat for around eight years. The reason I say its always full is after I changed out the filter on the tranny I put around eight quarts in and the day I drove it and would still have to rev high to move but ran a little better than now. The day after that it had a small leak that I thought was the pan but was coming from the shifter. Looks like a it lost a lot of fluid but started it up and checked at idle and was still full. Should I tune it up and how do I get rid of the lean. What's the best way to fix the boring on the shifter. Thank for the help fishy

This is exactly what mine drove like when my kickdown linkage was out of adjustment. Adjust it one way or the other and see what happens. Could be a simple fix.