ECU ground causing problems?
 

I had a problem with my 1991 convertible occasionally stumbling (I would lose all power for about one second) in left corners. I thought the problem might be a loose ground connection to the ECU, so I ran new ground wires to the ECU.

I haven't had the stumbling problem since I ran the new wires, however now the car seems to lose a lot of power above 6000 rpm. Sometimes the power will kind of pulsate at the higher rpms.

Could this be because the new grounds I ran don't have good connection?

Any help would be appreciated.

Probably a clogged or dirty fuel tank filter. Clean or replace the fuel tank filter. Pretty common, you may wish to use the search function next time found in the upper right hand corner of the page.

I am assuming that you are not loosing electrical power, but rather engine power?

Correct, I am losing only engine power. The electrical power seems fine.

clogged fuel tank filter (not the fuel filter, but it is the fuel tank filter).

Ya, the one in the TANK! ;)