I keep seeing on numerous forums the mention of the 15-18 tunnel? What the hell is it and where? Is it a path for your chopper that appears after beating the game or something? Thanks for any help you can give.

In Area 19 i belive, they are holding a guy hostage. If you keep hitting him with your bionic arm then you will make him talk and he will reveal two tunnels in the game. Make sure you don't shoot him though because you'll have to leave the area and come back to make him respawn.

I never got through any of the tunnels.  I got the secret item and never came back because they are absolutely ridiculous.

"I never got through any of the tunnels.  I got the secret item and never came back because they are absolutely ridiculous."

Well I got the items, but for 14-17 there's a platform with a door there.

I totally snagged the helmet in 15-18, but thought you had to finish the level in order to keep it.

Now I know that I'm totally wasting my time?!

*angry emote*

Just wondering but I got the Helmet from one of the tunnels and in that walkthrough, he mentioned 'the secret item' so if there is only one there, where is the third?