[Perfectlap]

There is no 97-99 engine blow out curse. The vulnerability your engine has is the same one most 97-2004 Boxsters have and to a lesser extent the 2005-2006's.
Nothing more than a leaky rear main seal (RMS) that will probably run you about a grand to replace, if your'e lucky you'll only need to do it once if at all. From purely word of mouth reporting it seems to affect a 1/3 of all 911's and Boxsters.
however, A small batch of 2.5 '97-'99 engines were made with engine blocks that allowed water to seep inside. But most didn't have this porosity issue.
The first generation Boxsters had more mechanical problems in general than the later years but that's just to be expected with any new model.

p.s.
keep the 16" wheels for autocross. If you can swing it and the tires need replacing see if you can get some 18" Carrera replicas from wheel dynamics.
They sell for about half the price of Factory 18" wheels. Not sure if you can run 18" wheels on a 98 though...