Unless you have removed the plugs I don't see how they cannot warranty it. If it was an exhaust manifold stud stripped out I could see that but, basic intake and exhaust mods shouldn't void that portion of your warranty. The only way I can see them even trying to argue is if they know you have a reflash and elevated boost pressures or you have changed or removed and reinstalled the plugs.

 

when i first bought my car i took it to get a turbo timer put on, after the install the mechanic said my car wasnt running right. I told them that when i dropped my car off it was fine but something was deffinitely wrong. So they decide to change the plugs and see if that was teh problem, however it wasnt so they changted them back...ever since then i have never touched my plugs so obviously they never tightened them all the way. I took it to the dealership and i came to find out that they had drilled through a wiring harness, short-cicuited the wire and fried my ECU. 1900 dollars later its fixed and they eventually paid me off. ever since then i never went back to them for any installations and now this happens about 9 months later...i know they arent going to pay for what happened but i am going to write them a letter and let them know what happened. One word of advice: Always be careful where you take your car to get worked on.

 

It's true. Remember, no one cares about your car but you. So, whenever you get something worked on, do what you can to inspect it. Even if someone just rotates your tires, re-torque the lugs yourself immediately.

I feel for you dude, good luck.

 

That sucks. Good luck.

 

So what did you end up doing with your cylinder head? I'm in the same situation with mine, happened just this morning with the same cylinder. I heard that there's a version of heli-coil that is meant for spark plug thread replacement. I'm not sure if I trust it though.