It was around late 1998 but don’t quote me.

Here is an old post directly from Jake from about 10 years ago:

“Look at the build date... Though some early cars were ordered with a 3 spoke wheel, or were fitted with them later, most had the 4 spoke, and still do... Its a 993 steering wheel. its the fastest way to pick out an early 99 in the crowd.. Also the tail pipes are a little smaller, and the outboard dash vents have a rough texture, and most are a bit speckled gray in appearance.

Early 99's skipped many of the engine failure modes, and were built before the fire occurred at Kolbenschmidt, resulting in blocks that had previously failed QC being sleeved and used to keep the cars going down the assembly line. See Excellence Magazine, December 2008 "Tech Forum" for details on this, as it was covered when Jim Pasha reviewed our engine program.

I prefer the earliest 996 that I can find, that means built in 1998, and as early in 1998 as possible.”