Check to make sure that your fan speed pullies are working propperly, if you would like to try something, unscrew the stopper nut to get a little bit more speed. Mark the prevous spot if this procedure dosenot work.
I've not had this experience, but . . . I'd suggest sizing your your machine up and down with a good one to see if you can see something different in the fan_sieve areas. How thick was this tinIJ If it was iron rather than tin . . . and with your symptoms . . . I'm inclined towards the fan cutoff as well.
Just a guess, is it the chaffer extensionIJ It is a "stair-step" piece of tin that fits with the fingers that help move the grain from the auger bed to the seives. When that piece breaks off, material can fall in front of the chaffer seive and perhaps even the shoe seive right into the clean grain auger. Seems to break off on a lot of long Seive combines. Hope this helps.
We put the same sieve back in after we fixed it. The piece of metal seemed to be pretty straight. We have tried opening the bottom sieve to get more air through but its just not the same as it used to be and according to the monitor the fan rpm runs as high as it always did. Thanks for your feedback.