yada

i have had my 2000 gs400 since october. i changed 1 cat and changed my mufflers to borla the week after i got my car. when i changed my cat i did it semi hasty as i didnt fully understand what people were doing to their exhaust systems i saw magnaflow cat back systems but mistakenly thought they were buying magnaflow cats then seperate mufflers. well i ran this and figured if i changed 1 cat i should change them both. Last week i got the matching cat installed and had the resonators deleted. i noticed first thing the car seemed down on power, from a standstill full throttle didnt kick the vsc indicator to come on nor did the car seem fast off the line. today on my way to work right around 200 miles from the cat change the CEL came on and gave me code P0446.

could my cat change affect the charcoal canister or evap system? i am also wondering why people may think my car is down on power? where would you go from my position?

this is the cat i changed to this cat is bigger then a stock unit and had to be welded on to fit. i didnt get bigger pipes they just fit this into my existing stock pipes

yada

no thoughts??

marshun

Have you reset the car by resetting the battery?

Was the loss of power immediate?

What have you tried?

yada

power loss was right away after leaving muffler shop. i havent done anything yet, i was thinking about resetting battery.

gsean400

It was the cats, the power loss is normal, your exhaust has too much free flow. I had immediate power loss when i straight piped my gs400 from the resonators back. It's gotta be your cats i would just go get new ones and try again, as for evap i think it might or might not be related. Usually those codes come up from loose lines either at the canister or in the front engine bay of the car. My conclusion is that your aftermarket cat is causing the loss in power cause its bigger in size or way to free flowing. Do you know if they kept the same size piping? When mine was done in 3 inch u COULD feel the power loss. Sounded nice tho. Could u post an exhaust video i wanna hear it

yada

Ya ill try to record a video later.

U went to autoscience in dfw area yesterday and a former park place lexys tech drove the car and felt it was fine. They used the same size pipe that was there before.

RoMiLex

With an 4.0L engine that makes 300hp factory it seems things are fairly efficient and at their peak already. Its a wonder anyone makes more power with any mods.

yada

i dont have a video of the exhaust from the outside but heres a video. these are all from the cockpit

marshun

well obd2 is more sensitive to mods. you have o2 sensors before and after the car and that measures the difference.

did you get it tuned?

im familiar with tuning but i dont know all the little nuances that come with different ecu's on different cars

brainsurge

I have to get a new Y-Pipe and consider going for bigger diameter...i want to go with 63,5mm out of the twc's and then join it to 70mm (and remove the #3 twc), then go to the stock exhaust...
would you consider this too big for the gs 430?

yada

No tuning, after doing only exhaust changes I didnt expect to need it.