Good Day, my wife's '03 Maxima seems to have an exhaust leak that I cannot find the source of. In the morning off a cold start, the exhaust sounds a little louder than normal when idling, but not much louder.

The real symptom begins when accelerating, as there is a loud semi metallic grinding raspy rumbling sound when accelerating while the car is still cold. Please note that this loud sound only lasts until the car is warmed up, and then it literally goes away. On a 30 minute commute, the sound may last 7-10 minutes. Once the car is fully warmed up and cruising down the highway, you hear nothing out of the ordinary. After shutting the car off, you hear a faint ticking sound coming from the engine bay.

I got under the car last weekend, checked the exhaust system from the y pipe back, and saw no holes or badly rusted sections. The only thing that I saw that was deteriorating was the y pipe heat shield breaking up around the flex section. So, I removed the heat shield thinking that that was my issue.
I saw, felt, nor heard any leaks.

Well, no such luck, as the sound is still there in full force while the car is accelerating while cold. I then took to this site, and google, and figure that it may be an exhaust leak at one of the gaskets on the manifold, or one of the gaskets between the manifold and pre-cats, or one of the gaskets between the pre cats and the y pipe, or a cracked manifold itself since the primary symptom is an exhaust leak that exists while cold, but seams to seal itself up once the engine gets up to normal operating temperature.

Now for my questions... Before tearing into this thing any further and ripping off manifold heat shields, does this sound like the logical next steps?
Do 5.5 Gen maxima's tend to have problems with cracked exhaust manifolds? Do they tend to have issues with broken manifold studs that cause exhaust leaks? Do they tend to have issues with gasket leaks on the manifolds? Is it common to have a leak between the y pipes and pre cats?
Also, could this sound be an actual symptom of pre cat failure? I don't have any CEL's or codes, but I am just wondering since the 5.5 gens are known for pre cat failures. This one has got me stumped, and is a PITA since the exhaust manifolds are hard to get to, and replacing everything exhaust related is cost prohibitive. Not to mention the fact that if I start tearing apart the exhaust things will definitely start to crumble as NE road salt corrodes everything. Any suggestions, or advice based on experience or hearsay??? Thanks in advance