ok... i searched a lot, but could not find sollution...

i bought an auto rx7 for my girlfriend. The guy i bought it from tried to do a auto -> manual conversion but lost interest in the project and sold it to me;
i fixed everything, changed all water/vacuum,etc hoses on the engine&tranny, put auto tranny back ... all in all everything is in the place and clean.
The car started with no problems, idles high (around 3k) but here is the problem:
i hold the brake pedal, i put the car in D or 1 or 2 or R (any gear different than P and N) and the revs drops and engine dies;

any suggestions? what should a look for? i found the double diafragm was not working so I changed it but still have the same problem

 

locked up torque converter?

 

^^^ that would make sense, that would be like dropping hte clutch with the brakes on

 

so the sollution for this is to change the torque converter?

is there any way to test if this is the real problem before taking off the tranny?