You can call me thick in the head if this topic has already been beat to death. I changed the OEM 12k old airfilter with a K+N filter on my '98 and now at highway speeds I have a noticeable bog on roll-on. It is most noticeable in 4th 5th and 6th gear at highway speeds. The spark plugs were replaced earlier this summer and I had no problems at that time. Now i know the vacuum signal line is hooked up to the correct nipple on the gas tank. Does this sound like a ruptured Vacuum diaphram at the petcock? There isn't any fuel dripping out of the nipple when I take the vacuum line off. I did add about 1.5 ounces of Sta-bil to a full take of 87 octane the last fill up but the stumble/surge existed before that fill up. Or does this sound like I need to rejet/shim my carbs. I can't believe an airfilter can make THAT much of a difference! I still have the stock exhaust installed as well. The engine will smooth out and pull to redline after it hits approx 8k rpm in each gear but it's dis-concerting waiting for the power to come back on-line when i needed it on an entrance ramp.
