Multiple Problems, Need some advice.

well a bad oil pump wont give you a starting problem but if the pump was bad maybe thats the rattle you hear. it might be also that you need to flush out your engine and see if the holes that drain your oil from the heads back to the crank are cloged also the oil pick up to the oil pump. if you still have the rattle after you install the oil pump and do a compleat flush it might be better to pull the engine out and have it checked it might be something aelse

Put a rebuilt engine in. I am sure that it is well over 100k and the previous owner didnt drive it like you are ( 4k shifts) and the engine was probably gunked up. The oil pressure was low enough while you were driving to have a lifter pump down ( skip and blinking CES light) and you had noises already. Damage done , Replace it.

Well, the car is in getting torn down atm, they are checking for the obvious stuff (timing chain and tensioner, main bearings for pitting or failure, etc etc etc). I thought about a possible intake failure but not leaking coolant or low and did not see any coolant on the dip stick when checking the oil. As for the 4K shift, I do not rod on the car, it shifts at 4K under any amount of load. I did get a tcc code when checking it along with the O2 codes, so there could possibly be a problem there causing it to shift at a higher RPM, really not sure. I will post once I get more info after the teardown.

That is not the normal shift point. There should a throttle control cable that should be adjusted also to bring the shift to the 25-2800 level. Whern you mash the pedal it should be around 4-4500 level. I think you will find a lot of debris around the oil pump pick up screen causing the loss of pressure. The problem is what kind of damage it has caused. Make sure you have the crankshafy "mic'd' to see if you can put bearings on it with out turning it. You might be able to if it did not run long on the '0' pressure time period. Good luck

Okay so tore the car down today. I must admit I lol'd abit when we found what happened. The previous owner did a timing chain, gears and oil pump in it. All the parts were in excellent condition. So, what was the problem you may ask. When he put everything back together he made sure everything was nicely placed, except the paper towel he left in the timing cover. Found it stuck in the main oil passage out of the pump. What are the odds. The crank, bearings and everything else made it though unscathed, no obvious damage and no knocking now. Rattle is still there, so next weekend it will be time to pull the inspection plate and check the flywheel and torque. I will probably just drive with the rattle if I cannot find an obvious problem and wait for the engine to go out then replace it with a rebuild or maybe something with a bit more play. Been doing alot of reading on the L67 swap and I have a small advantage over most. My mom lives in Australia so the Holden parts will be alot easier to obtain. For now the problem is solved though, thanks for your input all.

MIne had the problem as well, Change your muffler. It's been burnt up, probably has a hole.

Sorry May not be that severe, Check your pipes for gaps. Move them around to see how much room they move, replace or tighten grips. Although they're near the rear of the vehicle the sounds move as though it is in the front.

if the downpipes going to the muffler soon as they come off the motor and start to turn take a ball pin hammer and put a dent in it until the two walls touch and you will not have any rattle anymore fixed