Jet Hots are in, but now I'm having some problems. Under 1/4 or so throttle I seem to be getting some bad stumble. After I reach a certain RPM(around 3300 or so I think) it all seems to round out and drive extremely nice. I still have the stock exhaust with a flowmaster muffler after the Y. I installed the LT4 KM 2 days ago and it did help a bit, but it didn't clear up the problem. I noticed that a wire on the driver side header was pretty damn close to the header(possibly rubbing into it) and the plastic cover is melted some. I just noticed this tonight, so I haven't checked it out yet.

Also, before the header install I noticed I was having a loud knocking noise coming from the transmission area. I found it to be the infamous tranny mount and replaced that. Now, after the header install, I'm getting a knocking noise that sounds almost the same but isn't the tranny mount(maybe U joint?). I took it to a shop and they confirmed it wasn't the tranny mount and think that it has to do with the drivetrain. The knock comes under 1/4 or more throttle from a stop or slow roll and I've only noticed it once on a hard WOT shift.

Any suggestions on these problems? I could really use some help.

 

If it's coming from under the car, check the exhaust pipe where the y pipe meets the cat back. If those aren't tight, they will rattle at certain RPMs. Your stumble is probably false knock caused by the headers. Best way around this is a dyno tune.

 

I don't feel like spending $500 on a dyno tune, so would a MadZ28 or pcmforless tune fix my problem? Anybody else experience this? I went cruising a bit tonight and it feels like it's misfiring BAD! Very sluggish.

 

Melt plug wire on header? Loose or bad plug wire? If you reused your old wires you may want to replace them. Once wires get old and you move them around they can tend to look fine but really aren't. Start with that, next check for exhaust leaks. A pcm tune could help a little but a lt4 knock module may help more for about $30 or do both for max results. I would start with this stuff cuz it's free or cheap aside from a tune being a little pricey but well worth the $ anyway.

 

You most likely need a tune, I would reccomend MadZ28. Also, that plug wire is most likely burnt, and may be arcing.

 

I've got the LT4 KM and it helped for the first day, but now the missing has gotten worse. New AC Delco plugs and wires are on it. Is it possible that a plug is going to the wrong place?

 

Check your wires to make sure they are correct from the opti to the plug. Why do I recommend this? I did it on my install . As far as the hitting sound, check the y-pipe, cross member & torque arm. When I get on the car hard, the y-pipe hits the torque arm..... time for some exhaust work since I want a new cat-back anyway. I am still on the stock tune with a LT4 KM, a tune is coming when the cam goes in. Good Luck...

 

Ditto on the plugs and wires deal.

It's very common to miss a burning wire or to not fully seat the boot on the plug. I wouldn't be surprised if it was an issue with the plug wires.

Do you have any exhaust leaks?

 

if you didn't pull the plug's to take the headers out you may of cracked the ceramic portion of a plug.. It will have the same symptom's of a burnt wire...

 

I dropped it off at the place that did the install today and they told me that all of the plugs and wires were fine, none burnt or not on properly. They used some high temp loom on some of them to prevent burning. Also, I still have stock exhaust after the Y with a crappy flowmaster muffler.... could that be to blame for the problems I'm having? I do get a lot of back pressure and it backfires somewhat often.

Edit: Are 02 sims required if I get rid of the cats? I remember hearing this somewhere... doesn't sound right to me though.