Engine rpm's dropping slower
 

Hey Guys, I've searched the forum and came up empty handed. He's something that I've noticed.

I installed test pipes the other day and notice a distinct change of how fast the rpm's drop when I'm shifting. The rpm's are not dropping as fast as they were before hand.

Things I have thought of that may be causing the problem:

1. Less back pressure, but in my mind, this would allow the engine to evacuate air out of the cylinder faster meaning it should drop rpm's faster.

2. Tuning: the engine ecu has changed the timing/mixtures making the engine run different

3. This is a bit of a stretch but the test pipes I bought didn't fit well and may be putting unnecessary tension on the manifold and could potentially cause a slight leak, which may or may not cause any problems.


In addition the tuning, I also noticed the power delivery has changed. Before the test pipes, when I let off the throttle, the car would have a "jerky" (used lightly) motion, and then "jerky" again when putting the throttle back in. Now, coming off throttle and back on is much more smooth, almost like the ecu is, right at the end, keeping the throttle on a just a bit before shutting it off completely, compared to just dumping it all at once.

Also more info, (the idle wanders a bit at idle (+/- 100 rpm's). I know a need a tune at this point. (have plenum spacer and test pipes)

Another note, I did install a different style of test pipe before, and I do not remember these symptoms occurring.

If any of you guys have any ideas/have seen this before, please comment below.

Thanks!!