From ZDoom Wiki
A_ExtChase (bool domelee, bool domissile [, bool playactive [, bool nightmarefast]])
|Warning: The feature described on this page has been deprecated, and will no longer be supported or updated by the ZDoom developers. While some functionality may be retained for the purposes of backwards-compatibility, authors are strongly discouraged from utilizing this feature in future maps and to instead use A_Chase. Compatibility with future ZDoom versions is not guaranteed.|
- domelee: the monster can go to its Melee: state if true.
- domissile: the monster can go to its Missile: state if true.
- playactive: the monster plays its active sound if true.
- nightmarefast: the monster will move faster on skills with fastmonsters set if true.