After tons of searching to find a cure for the slow returning/dropping to idle RPM, and hearing advice that I needed to replace the flywheel, throttle body, computer tuning, and/or removing the balance shafts, etc..., I stumbled upon the "idle air restricter" from Fastforward Ltd. http://www.fastforwardltd.com/accessories.htm
Since nobody had any experience with the part, I figured I'd post up. Last week I received and installed it - I purposely waited to post until after a week of driving, just in case the computer would re-learn/compensate for the addition of the part.
(1) Cold Start
- Original - This never bothered me, but since there is a dramatic difference I figured I'd bring this up. When starting the car with the engine cold (keep in mind this is Vegas, garage temp is probably like 60), upon starting, the car's idle would immediately hit about 2,200 rpm, staying there for about 15 seconds, then start to gently fall to around 1,400.
- when cold, the RPMs climb only to about 1,400 rpm, then gently fall. Much nicer than original.
(2) Normal Driving
(engine warm) - Original - Under normal accelleration, if I were bringing the car to like 3,000 rpm, it'd take probably 1.5 sec for the RPM to drop to where I could let out the clutch on the upshift in order to make a smooth shift.
- The RPMs fall much quicker - not as quick as I'd like, but it's a noticeable - and welcome - change from the way it was originally. BTW, FastForward told me this, saying the idle air restrictor for the Zetecs provide a bigger difference than the ones for the Dura's.
For anybody with the slow-returning RPM (aka idle hang), I recommend this. Although it may not make the return to idle RPM perfect, it did make a noticeable improvement on mine. For under $100, this is probably a worthwhile investment.
With respect to FastForward, I spoke with both Nathaniel and Doug prior to buying the part - they were really cool and took the time to answer a lot of questions about the restrictor. Their customer service was excellent.