For a 1998, the ETC uses active (electronic) front struts and the base Eldorado uses passive (conventional) front struts. Both use, to my knowledge, rear air shocks as a rear spring supplement (again, ETC an active air shock and the base Eldorado a passive air shock).
Arnott sells replacement struts for both models (active and passive). If you have a base Eldorado, this is what you need (total parts cost less than $500):
http://www.arnottindustries.com/part...id6_pid36.html
If you have an ETC, this is what you need (total parts cost about $600):
http://www.arnottindustries.com/part...id6_pid49.html
Either way, you should be able to put FOUR new struts/shocks on your Eldorado for much less than $1000 (parts).
The Bridgestone Potenza G009 tires are probably relatively firm, being performance tires. You should always set your tire pressure cold (not hot). Start out at 30 psi cold, which is what Cadillac recommends (see the door jamb decal). 30 psi cold would equate to about 32-33 psi hot. 35 psi hot is only about 33 psi cold, which isn't that much over what Cadillac recommends. I typically run 35 psi cold in the front and 30 psi cold in the rear on both of my Sevilles...which is about 37 psi hot front and 32 psi hot rear. But again, set tire pressure COLD.
