1999 BMW 740i Base 8 Cyl 4.4L
bogs down if I try and punch it at the start and also at higher speeds if I try to accelerate quickly
If I am at a stand-still and want to punch it off the line it bogs down. It also does the same if I am trying to accelerate quickly at higher speeds.
Look at your fault codes...first and cheap test is to clean or have your mechanic clean the MAF sensor (easy!) and see if there is a difference. probably a MAF sensor, but could be many things. Have the codes read!