at WOT, my car wasn't performing right. I went to a local peformance shop and they told me that I should get a LT4 KM. Lucky they had one avaible.... installed it. And to my amazed, my car ran a great at WOT. :-)

Before the LT4 KM installed, I had MAC mid-length headers installed w/ flowmaster 3 inch exhaust.

Next.... planning to purchase a cutout. don't know if I should purchase an electric one or just the cutout. Big price difference.... $25 vs $180

 

change your fuel filter every 3 grand

 

Alright, well I have the Flowmaster exhaust system, but no headers... i will try to get the LT4 KM today. Other than that, do you have any other ideas what can cause my car to be losing alot of its performance? I have to check my fuel pressure because i never have, but would a low FP cause the vehicle to run decenly, but lose its performance? Plugs, coil, icm, fuel filter, all have less than 2k on them...the car runs fine, but maybe wires? who knows....any feedback would help alot...thanks~!

 

Try to get your car scanned....I heard Autozone does free testing only if they have the right tool! Check them out
What I did is check and replaced the least expensive part first

1. Coil
2. 02 Sensor
3. Cat. Converter
4. fuel filter
5. plug and wire
6. Opti change

This year, I am going to get my car dyno tuned, this will tell me what is really wrong with my car

 

you can also put a small guage on your exhaust and check for pressure. you shouldn't have much (< 1lb). if you rev your engine and the guage jumps to 6 or 8 lbs something is blocked downstream of the guage. they did it on a diy mechanic show this weekend. they put the guage right in the o2 sensor port.

david

 

to the original poster:

Where are you located? I have a set of stock manifolds and y-pipe with the cat laying around here. The y-pipe was replaced due to a clogged cat 2 years ago (for last emissions test) and was taken off the car when I installed headers novemberish. The car also sat at the top of my driveway for about 6 months, so I'd say theres about a good year of driving on it and I had absolutely no power loss while it was on.

If you're local we could arrange for a pickup...

Edit: I watched that show as well, helpful information IMO.

 

How can we tell that the Cat converter is clogged?

 

i am located in NJ....so i dont know how close to there you are...but today i jumped on the car...and i got this "rotten egg" smell for a minute or so, then it went away....also i jumped on it on the way from school, the RPMS went up, the car started to pull, but then quickly upshifted and lost all the power...i actually think it wanted to GO. Im trying to get an LT4 Knock module today...but everyone near me wants over 100 bucks and i see em for 40 and less all the time...so im gonna keep checking. 02 sensor...i never thought of that though...hmm...well anyone know what the heck the "rotten egg" smell was though? my cat? the car seems like it wants to go (i.e it revs out real nice) but then it just upshifts...could it be my Knock module playing with my timing when i rhomp on it? thanks!

 

just for diversity i am gonna step away from exhaust problem. im not saying that it isnt because it easily could be. when my opti first started to go the car ran real nice my first problem was the car wanted to go. i would have to press on the brakes hard to stay stopped at lights. most optis failing will have a lot more problems which mine did eventually. my car acted pretty much like you were describing for a couple weeks. just a thought. my first bet would be like there saying with exhaust but just keep in mind it might be something else.

 

I would agree that anything else could be the problem...but this car has been shall i dare say it...slow...for almost 3 months now. Id imagine the opti would have been shot by now. I actually fixed some of the problem, my "custom homemade" air intake was restricting my flow...i got my old stock stuff off the shelf, cut the end off that goes over the air filter, and i gained a bit of power back...but its still not where it should be. I am going to order the LT4 KM (like ive been sayin) but tonight i will make sure i get to it. I am hoping that Maybe, just maybe this could fix my problems, but if it doesnt im going to get the cat tested, and then most likely change the o2's. I am running out of ideas, anyone else have anything for me? thanks alot guys and gals!

 

Anybody have a part number for the LT4 KM??? Going to get one tom

 

Part #: 16214681

http://www.gmpartsdirect.com/

only $36 non NJ residence w/tax and shipping