When I bought my stang the mods started at 19K miles! I started with gears than proceeded to get a mac o/r H, mac CAI and some weld on flows! Then I got a shifter and pulleys! At 30k my A/C took a dump and I took it to my nearest ford house to get it checked out! Turned out my compressor was ****ed! The guyz fixed it without any problems and didn't say nothing about voiding the warranty!
...they even complimented my car and said it sounded Good!
.....it just depends where you take your car!
Miguel