Do you know what your converter slippage is? If the toque line was linear at 5500 RPM it looks like around 13% loss in torque but you should have had a loss in RPM as well.
The converter manufacture should be able to tell you what % slippage your converter has. If you data log engine RPM and drive shaft RPM and/or MPH in 3rd gear (1:1) the slippage can be calculated.
Did the manufacturer say if the lockup piston was billet as well or stock? That could be a huge variable but I really think the issue will be located in your tune.
Alan
Well guys, I appreciate the help so far. I am going to talk with my converter guy today about the lock-up piston, % slippage, etc. but the concensus seems to be that isn't the issue. I will also do some data logging over the next couple of days once I become a little more familiar with my SCT tuner and I'll post the results. So I guess in theory at least, it is plausible that everything is A-OK but just difficult to have the ideal conditions on that particular dyno?
I'm assuming that once you put the new converter in and did the j-mod, that you taped a pressure gauge to the windshield and drove around and dialed in your pressure, slip and torque curves and verfied your peak line pressure at WOT? Also did you look to see if the TCC is being commanded to lock in 3rd and if not where?
Other than the j-mod, did you make any other changes to the trans?
Well, I checked with my converter guy and lock-up piston is billet. He said that over the years he has come across cars acting weird on the dyno and drving and performing fine. Car pulls really good. I am going to get out there and drive it some over the next few days and try to data log some. Wish me luck!