2005 x5 reading misfire

I have a 2005 x5 I have taken it to the BMW dealer and they still can't not fix. Check engine lights flas and at times it will not go over 5 mph, but if the codes are reset it will be fine for a day or two. Codes are reading misfire on 5 and 7 also multiple misfires and running to rich, can someone please help me out with this please. Have replaced plugs and coils and they supposedly did a smoke test and still nothing... thank you