I have a 2001 BMW 525i where I just replaced the spark plugs and the cooling system inlet and outlet hoses and the intake manifold gasket. I got it all put back and started up but makes a whining sound and white smoke comes from the tailpipe. When I put it in drive and gave it some gas it hesitates then goes. The same goes for reverse.
The first thing I would suggest is that you check that the spark plug leads are fitted in the correct firing order. The order of these leads is vital to ensure smooth running.
Check the PCV system. In that car its called the CCV. Make sure to get the most recent model you can.
The whistling noise you are hearing is either a vacuum leak or a broken diaphragm in the CCV unit.