Welcome to the forum! Your 1999 has OBDII engine controls with the CSFI fuel injection system, totally different system than your '91. If you don't own a fuel pressure tester, you'll need one, as fuel pressure is critical on these engines. Most auto parts stores sell them for around $40 and Harbor Freight has an inexpensive one for under $20.
Check fuel pressure and leakdown first, then check for blue spark to all cylinders. Post your results and we will help you.