Advice wanted please: I presently have a 1988 Model 80 Q with 150,000 miles. I have an opportunity to purchase a 1991 Model 90 Q with 100,000 miles. I'm looking for advice on the desireability of the purchase, especially the differences in engines (going from 10V 2.3L engine to 20V 2.3L engine). Any advice would be appreciated. Thanks.