[6pack] TR6 Mistery Miss

[TR250Driver at aol.com]

Hi Guys,
I took the TR6 south to Oxford, OH for the 6-PACK Trials last week,  
probably less 600 miles total.  The Trials were great.  The Six had a  few issues. 
The first was a low RPM miss that caused her to chug some when  
accelerating.  Usually in 3rd or 4th with OD engaged but not  always.  She would chug 
some regardless of speed but usually below  2500 rpm's.  Once above that she 
seemed happier with only a few  chugs. Not enough of a problem to leave me 
on the side of the road but very  annoying. 
 
So I pulled the Bosch Platinum WR7dp plugs : #1 thru 4 look reddish  brown, 
#5 is brown & #6 is bright white.  I must be sucking in some air  back 
there, Huh?  From the manifold gasket?  I hate to just start  ripping into that 
w/o the wisdom of the List but the bright white is an  indicater of a lean 
condition in that cylinder, correct? What else  could it be?  The Six also 
got very hot once when I let her idle for 5  minutes which would confirm a 
lean condition.
 
I have had this problem before with the Six and also the TR250.  Seems  
like they both want to blow up manifold gaskets.  What am I doing  wrong?  I 
have tried the method of putting two gaskets on back to  back. I forget which 
way they go it's been so long.  I only have one on  now.
 
Any Tips are appreciated,
Darrell