Idle problem after adding spacer

I added a 1" trick flow phenolic spacer to my setup in the sig. Immediately after installing the spacer, the car will not idle it will just drop off to zero and die. It is not that it idles rough, it just simply will not idle. I can get it to idle if I set the idle to 1000-1100 but if I "blip" the throttle the idle does not return to the previous setting, it will continue to drop and die again. I have tried ajusting the TPS, the idle setting, replaced the IAC with one I had in the garage but nothing seems to help.....Any suggestions?

Another issue, before I added the spacer, I would get a surge or hesitation or occasionaly a backfire when accelerating slowly (normal street driving). However, under full throttle, I do not get the hesitation or backfire. I have tried adjusting timing, etc., but no real luck. What should the base timing be? This car seems to want a lot of timing.

Thanks for the help

Good suggestions but have already did them.
Checked all the vacuum lines...all ok,
I sprayed electrical cleaner around the spacer looking for leaks...made no difference.

I am running a 4 bank SCT chip. It was dyno tuned after it was stroked. I bought the car already strokerd and tuned. It was tuned with the 30# injectors. However, when I got the car it did not have the upper or lower intake or throttle body. Which is why I added the TFS intake. I added the spacer about 2 weeks after getting the car running with the new intake just to add more clearance around the valvle covers, etc.

Before I added the spacer, the car idled well enough to set the time with a timing light and removing the spout/pill. It seemed to run best 18-20 degrees but still had some hesitation during slow acceleration.