help my pug 106 sounds like ajumbo jet!!?

About a week ago engine management light came on my 106 independence x reg got it tested and ended up being lamba sensor fitted new sensor and all been good for a week now there is excessive noise when driving over 1500 literally sounds like a jumbo jet don,t know if this is any relevence but both faults occured after car been parked in heavy rain would be gratful for any suggestions thanks