+1 on the spark plug spacers. This is a link with some info. You can certainly get them cheaper from Advance auto etc.

http://www.3sx.com/store/comersus_viewItemBundle.asp?idProduct=28938

If your cat is blocked you may want to convert it to off-road use only. If the spacers do not work this is another option:


http://www.3sx.com/store/comersus_viewItemBundle.asp?idProduct=769

1992 VR4 12.5 @ 110 - SOLD
1993 Stealth RT/TT 11.4 @ 129 - SOLD
1991 VR4 9.2 @ 159 - Old Shop Car
1992 Stealth Twin Turbo ATX - SOLD
1990 Montero LS LWB - RIP
1995 Montero LS - RIP
1998 Montero
1992 Galant VR4 474/1000
2007 Prius