Im working on my brother in laws 87 buick, 3.8l. its surging terribly in drive, but revs great in P or N. I thought cat converter, but took it off and no change. I also checked EGR valve function and vacuum lines for leaks to no avail.
Anyone have any ideas ??...Id really like to get it going for them, they cant afford to take it in and need it for work.