Wall Street finished mixed in fickle trading today, with investors still unsettled about the US economy ahead of Friday’s employment report and only somewhat relieved about sliding commodities prices.

Wall Street managed a moderate gain in an erratic session as investors sorted through a downbeat Federal Reserve assessment of the economy and were also disappointed by a plan to bail out troubled bond insurer Ambac Financial Group Inc.

Wall Street bolted higher today after Standard & Poor’s affirmed its ratings for Ambac Financial Group Inc. and MBIA Inc., raising hopes that troubled bond insurers will emerge from the credit market crisis on solid footing. The Dow Jones industrials rallied nearly 190 points.

Wall Street staged a dramatic turnaround today, shooting higher in the last half-hour of trading amid word that a bail out plan for troubled bond insurer Ambac Financial could be announced next week.