Sr20 weird engine noise at 4200

[redpotatoes]

Just finished replaced a SR on a 180sx (sr20 S13). Engine seem to be running fine at idle but when reving the engine, close to 4200-5000 rpm, seems to cut. There is a noise coming from the engine. Hard to explain the noise in words but here goes "tratactactactratac...". Turbo is spooling and was running fine on it's original engine. Car is making boost but around 4200-5000 weird noise happens. Maf was also running ok and it's original engine. Any help would be appreciated. This happens only at WOT.

[Keith]

make sure the 4 nuts that hold the turbo to the manifold are tight and the gaskets good.