98es

Is this just a noise i can put up with or is it hurting anything by not getting it fixed????

I have a really odd problem that only occurs sometimes on my 1998 Es300 w/106,000 miles. It only happens when i'm driving at moderate to high speeds (ie on the highway) and when it's raining hard or has been raining for awhile. All the sudden it sounds like i have NO muffler. I can tell it has something to do with the exhaust because the noise changes with the engine RPM's and seems to be coming from the middle to rear of the vehicle. I've visually inspected the exhaust and don't see any holes or anything. It ONLY happens when it's raining, which really confuses me. I'm hesitant to take it to any shop because I haven't found a trusted mechanic in my area yet (Got ripped off about 1 month ago, paid $550 for a new IAC Valve!!). Any help would be GREATLY appreciated. Thanks!

My car is actually in the shop right now for that. It'll get progressively worse until you'll have no idle at all. My mechanic says it's the IAC motor like previously stated. He called it a motor but it sounds like it's more of a valve. My '98 ES300 has about 105k. He also said there was significant carbon build up around the throttle body due to EGR malfunction. He's charging 1.5 hours just to clean the throttle body. Total price for me was about $350. Was this too much??? Good Luck!