I have a 1998 Tahoe has 82000 miles on it. Just started this tapping when it sits over night and is started. Does not matter the temp. It sit in heated shop over night and done it today at startup.. Sounds like a lifter bleeding down. Would you replace the lifters now or drive it till gets worse or WHAT???? Could it be a piece of trash in lifter causing the problem??? Will Sea Foam or Mavel Mystery Oil help???