I'm loving the turbo slant 170 (draw through). It was obviously done by someone who sort of knew what they were doing but not entirely. I've made some improvements but I'm still trying to figure out why it bounces when coming back to idle. It will idle at a steady 700-800 rpms but when I rev it up (or let off the gas) it dips way down and bounces up to 1200+ and back down a good dozen times before it finally settles. Sometimes it dips so low it stalls. I also have a significant lag time between hitting the throttle and getting engine response. Is this the nature of the long path from carb through the turbo to chamber or do I have a leak somewhere that I can't find? There is an AFR sensor that shows (if it's accurate) my mixture is good so I'm assuming it's not a jetting or idle mixture issue but...?? It also came with a full exhaust and muffler. I'm planning to pull that and straight pipe it to make sure it's not clogging up the works but I'm assuming it's not really having much effect, if any, on performance. Any advice would be greatly appreciated!

Idle surge can be a lean AFR or too much timing. Note that even if the overall AFR is good, particularly on engines prone to fuel distribution issues, you may have some cylinders lean and some rich.

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Matt Cramer
1966 Dodge Dart turbo / EFI project

It could be the size of the turbo. Or, a issue I had with my initial draw thru turbo system was fuel not vaporizing properly in the inlet adapter between the carb and the turbo. I had to run hot water from the heater hoses to the bottom of the adapter. I actually had ice forming on the adapter at idle. No problem during driving conditions, just at idle.

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Charrlie_S
65 Valiant 100 2dr post 170 turbo
66 Valiant Signet 170 nitrous
64 Valiant Signet
64 Valiant 4dr 170
64 Valiant 4dr 225

Can you post some pictures of the setup. Without them, we are all guessing.