Troubleshoot

Have you checked the linkage at the throttle to see if it is binding or loose? There is a possibility it could be the TPS (Throttle Position Sensor), but it needs to be checked before replacement. One wire should have a constant 5 volts, one should vary from approximately.7 volts to 4.5 volts. The other wire is ground. If it changes voltage smoothly throughout the range of the throttle, the TPS will probably be OK. If it drops out or hangs in place a little, it is more than likely bad. The test is best performed with an analog style meter.

That sound could be a misfire/backfire thru intake? If TPS is original it might need changin. I use a standard cheap digital multitester on terminals after removed from car to check.