I have a TPI system off an 87 T/A that is completely disassembled except for the fuel rails. My question is, can the complete system be reassembled before installation on the engine or does the manifold have to be installed on the engine first and then the TPI system assembled. It seems that the bolts to hold the manifold on are to long and to hard to fit in because of the tuned ports and the fuel rails. Has anyone installed the TPI system already assembled onto the motor?

i do believe it will have to be assembled after the manifold it bolted on

The TPI set up has a specific order that it is assembled. Basically it is put together from the bottom up as virtually everything above blocks something below. I swapped an '86 TPI into my '69 Camaro and had to remove everything except the intake manifold and the EGR valve just to replace a leaky injector. I cannot recommend enough getting a copy of the factory manual for the engine as it has just about all the info on how the engine goes together and works. Watch the torque specs! Get the gaskets and seals ahead of time too. The parts stores should now carry them. I had to get mine from the dealer earlier and they cost me about $60.00. They should be cheaper now. Remember that the bolts are Torx type and not hex cap screws.
Good luck.