Not sure on the 93, but the older chevy's used a nylon tooth cam timing gear and they often wore out, it's possible that your's is worn and the chain may have jumped a tooth or two, put a timing light on it and see if your timing is ok or not then you can try adjusting it, check with a mechanic or dealer to see if this year has steel gears or nylon. One other thing is badly worn cam lobes, so the lifters are not opening the valves properly, you can pull your valve covers and check them for lift.
