OK this is my problem, i bought a 93 RX7 about 2 and a half months ago, in colorado, and drove it back no problem. Was fine all the way back and right when i got into town i started to get a hesitation around 5500 or 6k rpm. seems like a boost problem or some sort, the car also wont do this when it is cold, but after it warms up is seems to spool the primary turbo up fineand boosts up to about 11psi, but when the secondary comes on after the car is warm it will drop boost to about 8psi, i have no idea what the problem hope someone can help me!!!!!! oh i forgot today i was driving and it started to drop boost when the secondary came online, i pulled over to the side of the road and shut the car off with out letting the turbo timer, cool it off and started it right back up and the car was fine did, that two times today and seems to be fine right after shutting the car off and on

MODS: DP, Cat back w/out cat, boost controler, and pulley's

 

More than likely a leaking or popped-off vacuum line in the rats nest or maybe a bad check valve. Also check the lines going to the pressure tank which sits just in front of the upper intake manifold. I had a similar problem and after replacing two bad check valves and a leaky hose going to the pressure tank the problem went away.

 

my turbos were bad when I have that similar problem too.

The exhaust housing was crack