Over the Winter, I swapped out my 70 HP manifolds for the TTi headers (just headers, no other exhaust changes) in my combo listed below. I am still doing some minor tuning to the carb (IFR changes and jetting) so I have not been able to drive the car as hard as I did before this swap, but so far I am very happy with the results.
The off-idle response (torque) is the best part of the swap so far. The car is very responsive in the low range now and over the weekend I found another bonus. With the HP manifolds, the most my converter would flash too at 60mph in third gear cruise was 3500rpms. Over the weekend I noticed that it is now flashing to 3700rpms at 60mph. The swap definately made a "seat of the pants" difference on the bottom end and the flash rpms show some output change too, but I do not have any track information to pass forward to back this up.
1970 YO7 A66 [Canadian Export] F8 Challenger
340 (SL.P. 226/238@.050,270/288 dur,.538"/.528" w/Yella Terra 1.65 rockers, 9.7:1, 63cc Sidewinders (Bowl Ported),RPM intake, QF SS-750 Annular DP, MSD Street Fire Ign., & TTI's. 727/Dynamic 9.5" 3800, TF-2, & 3:91's