H/C/I Throttle Hang

[Bigred1]

Hey guys, I have a 08 c6z thats got a healthy Stage 4 Cam, Ported Heads, Ported MSD, Varraram intake and long tubes. when I had all those mods and a stock intake manifold the car drove around great! I put the MSD on it and got it retuned by the same tuner and now I get some throttle hang when I let off under 2k. it has been like 3 months since I got the MSD on it and I didn't really notice it until now. is there something in the tune I can adjust to help the throttle hang issue and let the rpms drop when I let off the throttle? it makes shifting around town a pain since the rpms do not drop fast enough.

attached is my current tune. the car idles great no starting issues pulls great and smooth. its the light throttle gear changing that is starting to bug me with the throttle hang. Especially putting around a parking lot? when I clutch in the revs jump up and hang for a bit around 1600-1800 before settling at idle.

at idle according to my boost/vacuum gauge I'm at around 7-8 inHG of vacuum at idle so I do not think its a vacuum leak.current 2_fuel density patch_1 - 11-5.hptcurrent 2_fuel density patch_1 - 11-5.hpt

[B52bombardier1]

A log would help here. My guess is a vacuum leak somewhere and we will see oddball readings for your Long and Short Term Fuel Trims in your log.

Rick

[danmw2003]

Vacuum leak

[Bigred1]

A log would help here. My guess is a vacuum leak somewhere and we will see oddball readings for your Long and Short Term Fuel Trims in your log.

Rick

Do you guys know how much vacuum I should be expecting to see on my gauge? Like I said when it’s warmed up at idle I see 7 to 8 inches of mercury on my gauge

I have no CEL’s for any lean codes.

[B52bombardier1]

My stock 1999 LM7 engine is a steady 18 inches Hg at idle. My vacuum-powered brake booster would be a hunk of useless ballast at 8 inches of mercury.

Rick

[Bigred1]

What size Cam? I know bigger cams lose vacuum at idle. I never had any brake issues with my vacuum booster at that level of vacuum.