I have a e46 bmw that has lost power in low rpm range I have done a head gasket leak test on radiator with the blue liquid and it passed. I have done a compression check and getting 175-180 on all cylinders. I believe it is a exhaust or vacuum leak. It could also possibly be fuel related. I am looking for a place to take it that will not try to up sell me and do an honest job. Thank you for any recommendations.