migrane

Hi I am new to this forum but have read almost every knock sensor problem there is on this forum.I have a 91 sr5 v6 3vze 4x4 pickup truck I bought it with a blown motor and a newly rebuilt motor in the bed from a friend.I installed the motor and put a lot of new parts under the hood but the problem is I get that code 52.did not replace the knock sensor not familiar with toyotas so didnt know.But checked the knock sensor for continuity and there is none going through so sensor is good. with sensor unplugged at top and codes reset runs good at idle and under 2000rpms but after 2000rpms the code returns.compression test good and all injectors are plugged in.How could I check the ecu?? Is the ecu the problem please help very stumped. Took it to toyota and they said knock sensor and exhaust was plugged but I had already knocked out all the exhaust components.They also didnt have a quote ready for me or didnt charge for 3 days of troubleshooting, so I dont think they know either.