After i installed my new cats and flowmaster exhaust i noticed my car runs kind of sloppy in low RPM's. like when i idle, it feels like it might almost stall. It only gets its power back in high rpms. Is there something i need to modify so my car can deal with the more open flow of the exhaust? thanks for the help

 

Is the car stock otherwise? What does the new exhaust consist of? Headers?

If all OEM equipment (sensors and emissions) was hooked back up properly I wouldn't think you'd need to modify anything. The car should run fine the way it is.

So it was running great before the exhaust upgrade and now it's not?

 

On my car the exhaust swap included everything but headers. One of my friends had the same problem with his 89 305 (all stock). All he did was switch out the muffler from stock to a 80 series flowmaster and experienced the same problem, a loss of power in low rpms with the feeling that the car is going to almost stall at idle.

Do you think there might be a leak somewhere causing this? maybe i should switch to those sleeve clamps insted of those horseshoe looking ones that comes in the american thunder kit.

 

The only time a leak would be an issue is if it was near or before the O2. That would cause the ECM to add fuel because there is extra oxygen in the exhaust.

I guess it could also be due to reduced backpressure increasing the volumetric efficiency. Does it still do this once the car is fully warmed?

 

I found that a small leak in the intermediate pipe was enough to affect the O2 readings, which in turn affected the way the engine ran and other sensor readings. So, double check for any small leaks - no matter how minor.

Lastly, a small tweak to your prom may not be a bad idea either as your overall operation has changed.

 

I believe that a loss in backpressure will translate into a slight loss in low end torque. Though, if you're noticing a significant power drop and idle problems, there's something else afoot. Like these guys are saying, an exhaust leak could cause confusion for the ECM.