Hi, welcome to the site mate
im Mountune 200, had 185 before it but never had the 165, feel like i missed out, but i did have pretty much a 165 equivalent modified fiesta ST before this one
Liams problem is something i had on my old car when i fitted the manifold the ford garage probably didnt think of it but im surprised that they didnt do it on yours Liam
when the cars cold you should be able to get your hand down the back of the engine and pull the heat shield away a little, make sure the engine hasnt been on for ages and the manifold will be very very hot very quickly
and the ST was made to be modded, pretty much everyone mods it even if its only some stripes or wheels there are not many fully standard ones on the road
have fun and if you want any help on any little jobs let me know i have taken mine and quite a few peoples cars on here apart in the past
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Red Escort 1.6LX
Then - Red Escort 1.4
Then - Silver Fiesta ST 170BHP
Then - White Fiesta ST MR200+
Now - Mitsubishi Evo IV Forged 2.3 500BHP
and Mondeo Mk3 2.0TDCI