So I have had my 91 TT for a couple of months now. Solved its limp mode issue with a MAF sensor from Z1 and have been enjoying this car in the evenings. As time went on and I would jump on it I noticed after about 30 to 40mins of driving I could hear a shutter like sound or possibly knocking when near a wall or near other cars and was wondering what I would need to do to see if this will be a big issue or how to go about fixing it. There was one time the oil was low in my altima back in the day and it sounded similar. I checked the oil in the z32 and its fine and I have coolant. I know it has the 500hp packaged confirmed from Z1 but I just wanted to know is some knock or lifter like noise ok or should I be worried and what can I do. Ask more questions im sure I detailed this poorly but im trying here. Slightly new to all of this. Thanks for the read everyone!

If it’s a knock it’ll be more apparent the lower you go in the engine. If it’s lifters you’ll hear more up top, sounds like a industrial sewing machine. Exhaust leaks can sometimes sound like lifter tick.

You could use thicker oil and see if that makes a difference.