The Sulfer smell is a give away
You have a catalytic converter issue. it may have a leak and the O2 sensor is reading a bad oxygen level and throwing the PCM into the default mode, causing an excessively rich condition which will cause the sulfer smell to get worse, (the 98 is notorious for this) your O2 sensor on the cat may be bad BUT dont be suprised if it isnt. the harness/connector to it are known to go bad as well. so get a service book such as a haynes from the library for info on how to check the sensor and connector and then check the harness id the connector shows bad... if both show good, CAREFULLY CUT the cat out and put in a TEMPORARY bypass tube with a jury rigged fitting for the O2 sensor (a hole cut in the pipe to fit the sensor with no leaks, NO SEALANTS!) and see what happens. if this corrects the condition your cat has gone bad or is blocked. Some people have had good luck cleaning them with steam, hot water being flushed through, acetone being misted onto the monolith and other carbon removal techniques, instead of just buying a new one online for between 150 to 250 dollars.
You noted that you did the tie wraps but did you use the deoxit? ad is the PCM getting a proper ground as well? these are two major points that need to be ensured.