it makes sense that the hood liner would increase engine compartment temperatures. The liner is a layer of insulation over the metal hood that could otherwise be conducting heat away from under the hood. The heat would then be removed from the hood by the air flowing over the top of the hood while you drive. Removing the liner gives you a coninent space to put stickers and other effects.

Negative effects of removing the hood liner are: the engine will cool off faster especially in cold weather after shutting the engine off. In case of an engine fire there is a higher chance of the hood suffering heat damage to the paint from the lack of insulation on the bottom of the hood. There will no longer be a convinent home for little critters like mice to live in the small spaces between the liner and the hood. In the case of an oil leak the hood liner can become oil soaked making it a fire hazard.

I'm sure I could think of more.

I feel sorry for the people who don't drink. When they wake up in the morning, thats the best they're going to feel all day - former President Lyndon B. Johnson