diff --git a/Manifest.toml b/Manifest.toml
index 21b502b..d745cbf 100644
--- a/Manifest.toml
+++ b/Manifest.toml
@@ -2,7 +2,7 @@
 
 julia_version = "1.9.3"
 manifest_format = "2.0"
-project_hash = "8cbb223fb1bc13003cdac808c2a640bd859706d1"
+project_hash = "38777d06b992a33542bab2fcfaa3bece835c0dbf"
 
 [[deps.Adapt]]
 deps = ["LinearAlgebra", "Requires"]
diff --git a/Project.toml b/Project.toml
index cff0c88..7201416 100755
--- a/Project.toml
+++ b/Project.toml
@@ -11,21 +11,13 @@ NPZ = "15e1cf62-19b3-5cfa-8e77-841668bca605"
 NumericalIntegration = "e7bfaba1-d571-5449-8927-abc22e82249b"
 PythonCall = "6099a3de-0909-46bc-b1f4-468b9a2dfc0d"
 QuadGK = "1fd47b50-473d-5c70-9696-f719f8f3bcdc"
-Requires = "ae029012-a4dd-5104-9daa-d747884805df"
 Statistics = "10745b16-79ce-11e8-11f9-7d13ad32a3b2"
 
-[extensions]
-BoltExt = "Bolt"
-
 [compat]
-Statistics = "1.7, 1.8, 1.9"
-QuadGK = "2.9"
 Interpolations = "0.14.7"
-NumericalIntegration = "0.2.0, 0.3.0"
-Requires = "1.3"
 NPZ = "0.4"
+NumericalIntegration = "0.2.0, 0.3.0"
 PythonCall = "0.9"
+QuadGK = "2.9"
+Statistics = "1.7, 1.8, 1.9"
 julia = "1.9"
-
-[extras]
-Bolt = "d94d39b4-3f51-4e5a-bfd8-f3b08e8f2b62"
diff --git a/ext/BoltExt.jl b/ext/BoltExt.jl
deleted file mode 100644
index 6263802..0000000
--- a/ext/BoltExt.jl
+++ /dev/null
@@ -1,31 +0,0 @@
-module BoltExt
-
-if isdefined(Base, :get_extension)
-    using Bolt
-else
-    using ..Bolt
-end
-
-function lin_Pk0(mode::Val{:Bolt}, cpar::CosmoPar, settings::Settings)
-    𝕡 = Bolt.CosmoParams(h = cpar.h,
-        Ω_r = cpar.Ωg,
-        Ω_b = cpar.Ωb,
-        Ω_c = cpar.Ωc,
-        A = cpar.As,
-        n = cpar.ns,
-        Y_p = cpar.Y_p,
-        N_ν = cpar.N_ν,
-        Σm_ν = cpar.Σm_ν)
-    bg = Background(𝕡)
-    𝕣 = Bolt.RECFAST(bg; Yp=𝕡.Y_p, OmegaB=𝕡.Ω_b,OmegaG=𝕡.Ω_r)
-    ih = IonizationHistory(𝕣, 𝕡, bg)
-    ks_Bolt = LinRange(-4, 2, settings.nk)
-    ks_Bolt = 10 .^(k_grid) 
-    pk0_Bolt = [plin(k,𝕡,bg,ih) for k in ks_Bolt]
-    pki_Bolt = linear_interpolation(ks_Bolt, log.(pk0_Bolt);
-                                    extrapolation_bc=Line())
-    pk0 = exp.(pki_Bolt(settings.ks))
-    return pk0
-end
-
-end # module
\ No newline at end of file
diff --git a/src/LimberJack.jl b/src/LimberJack.jl
index 8125be6..5097558 100755
--- a/src/LimberJack.jl
+++ b/src/LimberJack.jl
@@ -22,19 +22,9 @@ include("theory.jl")
 # c/(100 km/s/Mpc) in Mpc
 const CLIGHT_HMPC = 2997.92458
 
-if !isdefined(Base, :get_extension)
-    using Requires
-end
-
 function __init__()
     emupk_files = npzread(joinpath(artifact"emupk", "emupk.npz"))
     global emulator = Emulator(emupk_files)
-
-    @static if !isdefined(Base, :get_extension)
-        @require Bolt = "d94d39b4-3f51-4e5a-bfd8-f3b08e8f2b62" begin
-            include("../ext/BoltExt.jl")
-        end
-    end
 end       
 
 end # module
diff --git a/src/boltzmann.jl b/src/boltzmann.jl
index fcfd5ea..f6b774b 100644
--- a/src/boltzmann.jl
+++ b/src/boltzmann.jl
@@ -127,8 +127,15 @@ function lin_Pk0(mode::Val{:EisHu}, cpar::CosmoPar, settings::Settings)
     return pk0
 end
 
-lin_Pk0(mode::Symbol, cpar::CosmoPar, settings::Settings) = lin_Pk0(Val(mode), cpar, settings)
-lin_Pk0(@nospecialize(mode), cpar::CosmoPar, settings::Settings) = error("Tk mode $(typeof(i)) not supported.")
+function lin_Pk0(mode::Val{:Custom}, cpar::CosmoPar, settings::Settings; kwargs...)
+    ks_c, pk_c = kwargs[:pk_custom]
+    pki_c = cubic_spline_interpolation(ks_c, Pk_c, extrapolation_bc=Line())
+    pk0 = pki_c(settings.ks)
+    return pk0
+end
+
+lin_Pk0(mode::Symbol, cpar::CosmoPar, settings::Settings; kwargs...) = lin_Pk0(Val(mode), cpar, settings; kwargs...)
+lin_Pk0(@nospecialize(mode), cpar::CosmoPar, settings::Settings; kwargs...) = error("Tk mode $(typeof(i)) not supported.")
 
 function _get_kernel(arr1, arr2, hyper)
     arr1_w = @.(arr1/exp(hyper[2:6]))
diff --git a/src/core.jl b/src/core.jl
index b8788ea..912f0ff 100755
--- a/src/core.jl
+++ b/src/core.jl
@@ -249,7 +249,7 @@ Cosmology(cpar::CosmoPar, settings::Settings; kwargs...) = begin
     logk, nk = settings.logk, settings.nk
     ks = settings.ks
     dlogk = settings.dlogk
-    pk0, pki = lin_Pk0(cpar, settings)
+    pk0, pki = lin_Pk0(cpar, settings; kwargs...)
     # Compute redshift-distance relation
     norm = CLIGHT_HMPC / cpar.h
     chis = zeros(cosmo_type, nz_chi)
diff --git a/test/runtests.jl b/test/runtests.jl
index 6f285be..7b734f8 100755
--- a/test/runtests.jl
+++ b/test/runtests.jl
@@ -8,10 +8,12 @@ test_main=true
 if test_main
     println("testing main functions")
 end  
+#=
 test_Bolt = false
 if test_Bolt
     println("testing Bolt.jl")
-end    
+end   
+=# 
 extensive= false
 if extensive
     println("extensive")
@@ -769,6 +771,7 @@ if test_main
     end
 end  
 
+#=
 if test_Bolt
     Bolt_test_output = Dict{String}{Vector}()
 
@@ -832,4 +835,5 @@ if test_Bolt
         end      
     end
 end    
+=#