I think it s impossible for those critters to actually get "inside" the engine.....I think the only thing you have to really worry about is electrical prolems where they may have chewed on....they like to live where it is warm, and it sure does get warm at those pipes. Likely they started to live there till the first time you started the engine, then thought twice about it being a good place to live afterall, and moved inside the car. I would put the car on jack stands, get underneath with a really bright flashlight and study your wiring harnesses and hoses that may have been feasted on. I think you just found some "post crime" evidence. I think Z engine compartments must call to rats/mice....when I took my newly bought 91 to Greg at Specialty Z, they pulled the under car gravel shield off and there was an oil soaked rat critter on the shield. I think my car was lucky...he probably tried to jump through/climb through the accessory belt drive and was quickly terminated.
