Does the compressor on a ISL have to be timed? The braket that holds the PS pump to the engine came lose and oil started leaking between the compressor and front cover the bolts were lose a so i tightened them and it seems to have stopped leaking?
Yep
That's pretty common, especially with the 5.9 and 8.3 with compressor. The bottom rear support bracket for compressor will break or bolts get loose causing stress on the front structure/accessory drive housing. Which will and can cause severe oil leak between structure and block. Which means cam out and a bunch of work to reseal it. Yes it's timed IIRC.
Likely why they went to the rear mounted compressor on the ISB’s Never understood hanging a big heavy pump (air or hydraulic) on an aluminum cover like that. Had several 4BT’s that experienced failure because there was a big Cessna style pump that was driven through the timing gears.