INVESTMENT FIRMS HAVE 5.9 PCT OF PUROLATOR <PCC> A group of affiliated New York-base investment firms and funds told the Securities and Exchange Commission they have acquired 453,300 shares of Purolator Courier Corp, or 5.9 pct of the total outstanding. The group, led by Mutual Shares Corp, said it bought the stock for investment purposes. It also said it is studying the 35 dlr a share leveraged buyout offer made by Purolator managers and E.F. Hutton LBO Inc but has not decided whether it will tender its stock in the offer. The group said it has held talks with the Hutton LBO group before and may do so again.