I know some of this issue has been covered in tangent discussions about Edelbrock's Pro Flo 4 and I've read where some people have had a similar issue but I'm going to ask definitively if anyone has had the problem of not being able to set Advance Timing to greater than an 20 degrees with a Pro Flo 4 on a small block? I have a stroker 408, Hughes Hydrualic lifter flatappet 228/232 @ 50 cam, 727 with a 9' convertor and 3000 stall and I'm running Trick Flow 190 heads. No matter where I try to set the timing, if it is above 20 degrees the car stumbles, backfires and vibrates horribly, especially when accelerating hard, with the worst vibrating beginning about 3000. I have adjusted the fuel via Fuel Modifiers to compensate thinking it might be a fuel issue, but that had no effect. I have varied the Idle Timing from 12 to 18 degrees. I've adjusted the vacuum advance from 0 to 10 and if I go above 5 the engine has a similar reaction: it misfires, stumbles and causes the car to vibrate. I'm running Mag 5028 but I've had the same issues with Maps 5029 and 5030. The engine should be making considerably more power than it does and I blame that on the low timing it will accept without the vibrations. Any input would be appreciated, especially if you've had a similar issue and you were able to resolve it.