msmmce1

Hello I have a 1997 tacoma 2.4 and I replaced the cracked stock exhaust manifold about a year and a half ago with a Dorman replacement and recently it is has started to sound like an exhaust leak under the hood only when the engine is hot. I have removed the heat shield and retorqued the bolts and can't visually find any cracks but the problem persists. Is it possible for there to be a crack that I can't see when cold causing the problem?
Thanks
Scott